{"id":17022,"date":"2021-05-27T17:18:48","date_gmt":"2021-05-27T09:18:48","guid":{"rendered":"https:\/\/smartairfilters.com\/?page_id=17022"},"modified":"2025-10-29T22:11:28","modified_gmt":"2025-10-29T14:11:28","slug":"data","status":"publish","type":"page","link":"https:\/\/smartairfilters.com\/en\/data\/","title":{"rendered":"Air Pollution and Air Purifier Data"},"content":{"rendered":"<div class=\"gb-grid-wrapper gb-grid-wrapper-644c8759\">\n<div class=\"gb-grid-column gb-grid-column-1932fe8e\"><div class=\"gb-container gb-container-1932fe8e\"><div class=\"gb-inside-container\">\n\n<h2 class=\"gb-headline gb-headline-8d3cde74 gb-headline-text\">Welcome to the Smart Air Data Center<\/h2>\n\n\n\n<p>Here\u2019s where you\u2019ll find answers to questions about air quality, air pollution and air purifier curated by Thomas Talhelm, founder of&nbsp;<a href=\"https:\/\/smartairfilters.com\/\">Smart Air<\/a>.<\/p>\n\n\n\n<h4 class=\"gb-headline gb-headline-d5017d12 gb-headline-text\">Let&#8217;s get started<\/h4>\n\n\n\n<div class=\"gb-headline gb-headline-04209925 gb-headline-text\">1. <a href=\"#using-your-smart-air-purifier\">Using your Smart Air purifier<\/a><br>2. <a href=\"#air-pollution-in-china\">Air pollution in China<\/a><br>3. <a href=\"#tests-and-comparison\">Tests and comparisons<\/a><br>4. <a href=\"#gases-and-carbon\">Gases and carbon<\/a><br>5. <a href=\"#more-faqs\">More FAQs<\/a><\/div>\n\n<\/div><\/div><\/div>\n\n<div class=\"gb-grid-column gb-grid-column-6d3ad1b4\"><div class=\"gb-container gb-container-6d3ad1b4\"><div class=\"gb-inside-container\">\n\n<h4 class=\"gb-headline gb-headline-2a54ed51 gb-headline-text\" id=\"using-your-smart-air-purifier\">Using your Smart Air purifier <\/h4>\n\n\n\n<p><a href=\"#1.1\">Is the air coming out of the air purifier clean?<\/a><\/p>\n\n\n\n<p><a href=\"#1.2\">Is the air coming out of the air filter enough to actually clean air in the entire room?<\/a><\/p>\n\n\n\n<p><a href=\"#1.3\">How well does it perform compared to expensive air purifiers?<\/a><\/p>\n\n\n\n<p id=\"q4button\"><a href=\"#1.4\">How long will the HEPA filter last?<\/a><\/p>\n\n\n\n<p id=\"q5button\"><a href=\"#1.5\">How large a room can the air purifier clean?<\/a><\/p>\n\n\n\n<p id=\"q6button\"><a href=\"#1.6\">Do you have to run it all day?<\/a><\/p>\n\n\n\n<p id=\"q7button\"><a href=\"#1.7\">Can I turn off my air purifier while I sleep?<\/a><\/p>\n\n\n\n<p id=\"q8button\"><a href=\"#1.8\">How loud is the air purifier?<\/a><\/p>\n\n\n\n<p id=\"q9button\"><a href=\"#1.9\">Why can\u2019t I just order the filters and fans myself?<\/a><\/p>\n\n<\/div><\/div><\/div>\n\n<div class=\"gb-grid-column gb-grid-column-e2440f8a\"><div class=\"gb-container gb-container-e2440f8a\"><div class=\"gb-inside-container\">\n\n<h4 class=\"gb-headline gb-headline-4ecd590f gb-headline-text\" id=\"air-pollution-in-china\">Air pollution in China<\/h4>\n\n\n\n<p><a href=\"#2.1\">How much does outside air affect indoor air?<\/a><\/p>\n\n\n\n<p id=\"q11button\"><a href=\"#2.2\">Is smoking worse than outdoor air pollution?<\/a><\/p>\n\n\n\n<p id=\"q12button\"><a href=\"#2.3\">Is air pollution just a Beijing problem?<\/a><\/p>\n\n\n\n<p id=\"q13button\"><a href=\"#2.4\">How does air pollution change throughout the day?<\/a><\/p>\n\n\n\n<p id=\"q14button\"><a href=\"#2.5\">Does Chinese New Year affect inside air quality?<\/a><\/p>\n\n\n\n<h4 class=\"gb-headline gb-headline-f67299bf gb-headline-text\" id=\"tests-and-comparison\">Tests and comparisons<\/h4>\n\n\n\n<p id=\"q15button\"><a href=\"#3.1\">What happens to a room with no air purifier in it?<\/a><\/p>\n\n\n\n<p id=\"q18button\"><a href=\"#3.2\">Has anyone else tested the DIY air purifier?<\/a><\/p>\n\n\n\n<p id=\"q19button\"><a href=\"#3.3\">Are all DIY air purifiers the same?<\/a><\/p>\n\n\n\n<p id=\"q20button\"><a href=\"#3.4\">Are DIY air purifiers still cheap in the long run?<\/a><\/p>\n\n\n\n<p id=\"q21button\"><a href=\"#3.5\">Are cheaper HEPA filters possible?<\/a><\/p>\n\n<\/div><\/div><\/div>\n\n<div class=\"gb-grid-column gb-grid-column-5b982335\"><div class=\"gb-container gb-container-5b982335\"><div class=\"gb-inside-container\">\n\n<h4 class=\"gb-headline gb-headline-5ee91263 gb-headline-text\" id=\"gases-and-carbon\">Gases and carbon<\/h4>\n\n\n\n<p id=\"q22button\"><a href=\"#4.1\">Do activated carbon filters really work?<\/a><\/p>\n\n\n\n<p><a href=\"#4.2\">Does everyone need a carbon filter?<\/a><\/p>\n\n\n\n<p><a href=\"#4.3\">Do I still need a HEPA filter?<\/a><\/p>\n\n\n\n<p id=\"q23button\"><a href=\"#4.4\">Does adding an activated carbon filter reduce particulate effectiveness?<\/a><\/p>\n\n\n\n<p id=\"q24button\"><a href=\"#4.5\">Can an activated carbon filter remove formaldehyde?<\/a><\/p>\n\n\n\n<h4 class=\"gb-headline gb-headline-1daa6467 gb-headline-text\" id=\"more-faqs\">More FAQs<\/h4>\n\n\n\n<p id=\"q25button\"><a href=\"#5.1\">Does air conditioning bring in dirty outside air?<\/a><\/p>\n\n\n\n<p id=\"q26button\"><a href=\"#5.2\">Are our particle counters the same as government air monitors?<\/a><\/p>\n\n<\/div><\/div><\/div>\n<\/div>\n\n\n<hr class=\"wp-block-separator has-css-opacity is-style-wide\"\/>\n\n\n\n<h3 class=\"gb-headline gb-headline-898bd3d3 gb-headline-text\" id=\"1.1\">Is the air coming out of the air purifier clean?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>This is the easiest question to answer, and we can do it by holding the particle counter in front of the unit and watching the numbers drop. Here&#8217;s a video of me doing just that:<\/p>\n\n\n<figure class=\"wp-block-embed-youtube wp-block-embed is-type-video is-provider-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio lyte-align aligncenter\"><div class=\"lyte-wrapper\" title=\"Original DIY Air Purifier Live Test with Dylos Particle Counter | Smart Air\" style=\"width:640px;max-width:100%;margin:5px auto;\"><div class=\"lyMe hidef\" id=\"WYL_fRYYrHSxTGo\" itemprop=\"video\" itemscope itemtype=\"https:\/\/schema.org\/VideoObject\"><div><meta itemprop=\"thumbnailUrl\" content=\"https:\/\/smartairfilters.com\/wordpress\/wp-content\/plugins\/wp-youtube-lyte\/lyteCache.php?origThumbUrl=https%3A%2F%2Fi.ytimg.com%2Fvi%2FfRYYrHSxTGo%2Fmaxresdefault.jpg\" \/><meta itemprop=\"embedURL\" content=\"https:\/\/www.youtube.com\/embed\/fRYYrHSxTGo\" \/><meta itemprop=\"duration\" content=\"PT2M3S\" \/><meta itemprop=\"uploadDate\" content=\"2017-09-13T07:03:15Z\" \/><\/div><div id=\"lyte_fRYYrHSxTGo\" data-src=\"https:\/\/smartairfilters.com\/wordpress\/wp-content\/plugins\/wp-youtube-lyte\/lyteCache.php?origThumbUrl=https%3A%2F%2Fi.ytimg.com%2Fvi%2FfRYYrHSxTGo%2Fmaxresdefault.jpg\" class=\"pL\"><div class=\"tC\"><div class=\"tT\" itemprop=\"name\">Original DIY Air Purifier Live Test with Dylos Particle Counter | Smart Air<\/div><\/div><div class=\"play\"><\/div><div class=\"ctrl\"><div class=\"Lctrl\"><\/div><div class=\"Rctrl\"><\/div><\/div><\/div><noscript><a href=\"https:\/\/youtu.be\/fRYYrHSxTGo\" rel=\"nofollow\"><img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/smartairfilters.com\/wordpress\/wp-content\/plugins\/wp-youtube-lyte\/lyteCache.php?origThumbUrl=https%3A%2F%2Fi.ytimg.com%2Fvi%2FfRYYrHSxTGo%2F0.jpg\" alt=\"Original DIY Air Purifier Live Test with Dylos Particle Counter | Smart Air\" width=\"640\" height=\"340\" \/><br \/>Watch this video on YouTube<\/a><\/noscript><meta itemprop=\"description\" content=\"Live test of Smart Air Original DIY Air Purifer by Thomas Talhelm. Watch those particle counts drop to zero! smartairfilters.com smartair.taobao.com Smart Air is a social enterprise dedicated to helping people protect themselves from the harms of air pollution through education and low-cost purifiers. \u2022 Subscribe: https:\/\/www.youtube.com\/SmartAirFilters \u2022 LinkedIn: https:\/\/www.linkedin.com\/company\/smart-air-filters\/ \u2022 Facebook: https:\/\/www.facebook.com\/smartairfilters \u2022 Twitter: https:\/\/twitter.com\/SmartAirFilters \u2022 Instagram: https:\/\/www.instagram.com\/smartairfilters\/ \u2022 Volunteer: https:\/\/smartairfilters.com\/en\/volunteer-at-smart-air\/ \u2022 Shop: https:\/\/smartairfilters.com\/en\/shop\/ For business enquiries, email us directly at info@smartairfilters.com.\"><\/div><\/div><div class=\"lL\" style=\"max-width:100%;width:640px;margin:5px auto;\"><br\/><span class=\"lyte_disclaimer\">Subscribe to <a href=\"https:\/\/www.youtube.com\/smartairfilters?sub_confirmation=1\">Smart Air on YouTube<\/a> <img decoding=\"async\" src=\"https:\/\/smartairfilters.com\/images\/smartair_youtube.ico\" alt=\"Smart Air Youtube\"\/><\/span><\/div><figcaption><\/figcaption><\/figure>\n\n\n<div class=\"gb-headline gb-headline-0de0e675 gb-headline-text\">(Can&#8217;t see the video? Watch it on <a href=\"https:\/\/www.youtube.com\/watch?v=fRYYrHSxTGo\">YouTube<\/a> or <a href=\"http:\/\/v.youku.com\/v_show\/id_XODI2MDMyNzky.html\">Youku<\/a>.)<\/div>\n\n\n\n<h5 class=\"gb-headline gb-headline-6b44581e gb-headline-text\">Conclusion: <\/h5>\n\n\n\n<p class=\"has-black-color has-text-color\">Yes, air coming out of the air purifier is clean.<\/p>\n\n\n\n<div class=\"gb-headline gb-headline-33877ee2 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-1376f137 gb-headline-text\" id=\"1.2\">Is the air coming out of the air filter enough to actually clean air in the entire room?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>To answer this, I set up the <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">particle counter<\/a> on one side of my 13.5m\u00b2 Beijing bedroom and put the DIY filter on the opposite side of the room. Here&#8217;s what the air filter did in one hour:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/pm25minutes.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>And over the course of eight hours:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" src=\"\/images\/pm25hours.png\" alt=\"image\"\/><\/figure><\/div>\n\n\n<p>The particle counter also gives data on PM0.5 micron particles \u2014 even smaller than the PM2.5 micron reading. Here&#8217;s what that looks like over eight hours:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/pm5hours.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-aaeb6ac8 gb-headline-text\">Conclusion: <\/h5>\n\n\n\n<p>Yes, the clean air from the DIY air filter is cleaning the entire room.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/cn\/en\/our-data-does-the-smart-air-diy-purifier-work\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/smartairfilters.com\/en\/blog\/supplemental-data-testing-methodology-for-diy-purifier\/#method2\">If you\u2019re a data nerd like us, click here for the raw data and more details on the methods.<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-c063ae71 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-25fcbcce gb-headline-text\" id=\"1.3\">How well does it perform compared to expensive air purifiers?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Pretty well.<\/h5>\n\n\n\n<p>After a few kind souls donated a <a href=\"http:\/\/www.blueair.com\/India\/en\/products\/270E\/\">BlueAir 203\/270E<\/a> (<a href=\"http:\/\/item.taobao.com\/item.htm?spm=a230r.1.14.1.OUhGOM&amp;id=35713354718\">3,600 RMB<\/a>), a <a href=\"http:\/\/www.p4c.philips.com\/cgi-bin\/dcbint\/cpindex.pl?ctn=AC4072\/00&amp;scy=cn&amp;slg=en\">Philips AC4072<\/a> (<a href=\"http:\/\/detail.tmall.com\/item.htm?spm=a230r.1.14.37.e6J1V9&amp;id=10217677358&amp;sku_properties=\">3,000 RMB<\/a>), and an <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a230r.1.0.0.BRpEd5&amp;id=39877587913&amp;ns=1#detail\">IQAir Health Pro<\/a> (<a href=\"http:\/\/item.taobao.com\/item.htm?spm=a230r.1.0.0.BRpEd5&amp;id=39877587913&amp;ns=1#detail\">8,000 RMB<\/a>) I was able to test the DIY against expensive brands in the same room, for the same amount of time, with the same particle counter.<\/p>\n\n\n\n<p>To do that, my collaborator Anna ran 11 overnight tests with the BlueAir, 9 tests with the Philips, and 11 tests with the IQAir. I calculated effectiveness as percent reduction in particulates from the room air. Anna tested the air before she turned on the air filter, and then set the particle counter to take hourly measurements of the air in her 15m2 Beijing bedroom. Anna used the highest setting on each filter.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/AverageEffectivenessEN.png\" alt=\"image\" style=\"width:560px\"\/><\/figure><\/div>\n\n\n<p>All of the filters significantly reduced particulates, but the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7525708604.2.KkyOmq&amp;id=36350325474\">470 RMB<\/a> <a href=\"http:\/\/smartairfilters.com\/cn\/en\/product\/cannon-diy-air-purifier\/\">Cannon air purifier<\/a> removed as many particles as the highest-performing big brand. Even the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7525708604.4.KkyOmq&amp;id=35171288192\">200 RMB<\/a> <a href=\"http:\/\/smartairfilters.com\/cn\/en\/product\/diy-1-1-air-purifier\/\">Original DIY air purifier<\/a> was only 6% behind the Blue Air on the .5 micron particles and 4% behind on the 2.5 micron particles.<\/p>\n\n\n\n<p>Among the different brands, there seems to be no relationship between price and particulate removal:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/EffectivenessvsPriceEN.png\" alt=\"image\" style=\"width:560px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-5ccdb165 gb-headline-text\">Conclusion: <\/h5>\n\n\n\n<p>You can remove particulate pollution from the air in your home and pay far less than the cost of a Blue Air, Philips, or IQAir.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/cn\/en\/our-data-does-the-smart-air-diy-purifier-work\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/smartairfilters.com\/en\/blog\/supplemental-data-testing-methodology-for-diy-purifier\/#method3\">If you\u2019re a data nerd like us, click here for the raw data and more details on the methods.<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-e94068a6 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-e9bfdee0 gb-headline-text\" id=\"1.4\">How long will the filter last?<\/h3>\n\n\n\n<p><strong>For the DIY purifier, I recommend replacing your filter after 140 days of use at 8 hours a day.<\/strong><\/p>\n\n\n\n<p>For our other purifiers, check out the following links to the HEPA lifespans of our <a href=\"https:\/\/smartairfilters.com\/learn\/smart-air-knowledge-base\/whats-the-lifespan-of-the-sqairs-hepa-filter\/\">Sqair<\/a>, <a href=\"https:\/\/smartairfilters.com\/en\/blog\/blast-mini-hepa-filters-lifespan\/\">Blast Mini and Blast<\/a>.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/longevityprogression.png\" alt=\"\" style=\"width:600px\"\/><\/figure><\/div>\n\n\n<p>One of the biggest questions when I started doing the DIY was how long the HEPAs last. Rather than just give people a nice-sounding answer, I wanted to see what the data says, so I had <a href=\"http:\/\/smartairfilters.com\/en#about\">Gus<\/a> turn on his <a href=\"http:\/\/particlecounting.tumblr.com\/post\/64308970069\/the-newer-cuter-diy-filter\">Original DIY<\/a> every day in his 12.3m\u00b2 Beijing bedroom and track how effective it is each day in real Beijing air. <\/p>\n\n\n\n<p>Around&nbsp;<a href=\"http:\/\/particlecounting.tumblr.com\/post\/91439902176\/how-long-do-smart-air-hepas-last-longevity-test-day\">Day 100, effectiveness dropped 4%<\/a>. Around another&nbsp;<a href=\"http:\/\/particlecounting.tumblr.com\/post\/96834332359\/hepa-longevity-test-170-days\">Day 140, effectiveness dropped another 5-10%<\/a>. Read the full article <a href=\"https:\/\/smartairfilters.com\/data1\/how-long-does-a-smart-air-filter-last\/\">here<\/a>.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-de2fc1a8 gb-headline-text\">Conclusion: <\/h5>\n\n\n\n<p>In real Beijing air, the Smart Air HEPA lasted at 100 days at about 8 hours a day at full effectiveness (729 hours to be exact). It lasted through 140 days (1,028 hours) with a slight 4% drop, which is when I would change the filter.<\/p>\n\n\n\n<div class=\"gb-headline gb-headline-894c2ba0 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-c6f07569 gb-headline-text\" id=\"1.5\">How large a room can it clean?<\/h3>\n\n\n\n<p><strong>The Original DIY is effective in normal-sized bedrooms (up to 15 m\u00b2) and the Cannon can handle larger spaces.<\/strong><\/p>\n\n\n\n<h5 class=\"wp-block-heading\">Here&#8217;s a test of the Cannon in a 30.5 m\u00b2 room:<\/h5>\n\n\n\n<p>In the summer of 2015, I lived in a large 4-bedroom apartment in Beijing, with a 30.5m\u00b2 living room. I tested <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7525708604.1.3ObdBt&amp;id=36350325474\">the Cannon<\/a> six times on high and tracked particulates with <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">a Dylos particle counter<\/a>. Each test lasted at least three hours.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/d567b17497530633c7561a399b21d109\/tumblr_inline_nhggrew2a41s4lgm1.jpg\" alt=\"\"\/><\/figure><\/div>\n\n\n<p>I calculated the percentage reduction in particles from the first hour to the last hour.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" src=\"http:\/\/33.media.tumblr.com\/7346af34e1759735d5455f2126928c84\/tumblr_inline_nhghk8nHD71s4lgm1.png\" alt=\"\"\/><\/figure><\/div>\n\n\n<p>This test also serves as an important extension of the other <a href=\"http:\/\/particlecounting.tumblr.com\/post\/98424809631\/new-tests-can-a-450-rmb-diy-remove-as-much-particulate\">room tests<\/a> because:<\/p>\n\n\n\n<p>1. These tests were run in the daytime. Several people have the intuition that pollution goes down at night because people are less active and fewer cars are on the road (but the data shows that intuition is false \u2014 PM2.5 pollution is worst in the middle of the night in Beijing).<\/p>\n\n\n\n<p>2. These tests were run while people were moving around in the room and opening the door to the outside. This is more conservative than the nighttime tests because the Cannon has to fight influxes of outdoor air.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-431717bc gb-headline-text\">Results<\/h5>\n\n\n\n<p>Over six tests, the Cannon removed 92% of .5 micron particles and 89% of 2.5 micron particles even with people moving around and opening doors.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/cannonbigroomcompare.png\" alt=\"\" style=\"width:300px\"\/><\/figure><\/div>\n\n\n<p>In previous tests, 2.5 micron reductions were <a href=\"http:\/\/particlecounting.tumblr.com\/post\/98424809631\/new-tests-can-a-450-rmb-diy-remove-as-much\">usually slightly larger than .5 micron reductions<\/a>, so it&#8217;s a little surprising that the 2.5 micron reduction was 3% lower than the .5 micron reduction. My guess is that this is because people were moving in the room, and human movement affects the 2.5 micron readings much more than the .5 micron readings.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-4c913056 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>The Cannon can clean rooms at least 30.5m\u00b2, which puts it above the 22.3m\u00b2 Blue Air recommends for their <a href=\"http:\/\/us.blueair.com\/product\/blueair-203\/blueair-203-technical-specs\">3,6000 RMB 203 model<\/a>.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/diy-air-purifiers-clean-large-rooms\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-229856e3 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-4c317494 gb-headline-text\" id=\"1.6\">Do you have to run it all day?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">No.<\/h5>\n\n\n\n<p>Some purifier companies recommend running your purifier all day. But is that really necessary? If so, isn&#8217;t that a big waste of your filters and energy?<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-5d2e7977 gb-headline-text\">Method<\/h5>\n\n\n\n<p>To get to the bottom of it, I set a <a href=\"http:\/\/smartairfilters.com\/#compare\">Smart Air Cannon<\/a> on a timer to turn on for two hours everyday in a 13.5m2 Beijing bedroom, and I put a <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">particle counter<\/a> in the room to take measurements every minute. I did the test while I was on vacation, so there was no influence of me opening and closing doors.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-f7d717b8 gb-headline-text\">Results<\/h5>\n\n\n\n<p>After six days, I came back and saw how long it took to <a href=\"http:\/\/smartairfilters.com\/#compare\">the Cannon<\/a> to clean the air each time it came on. Here&#8217;s what six days of data looked like for the small .5 micron particles:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/shanghaitesttime.png\" alt=\"\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>Over the six test days, the air in Beijing became progressively worse. But on each day, it was clear when the Cannon turned on and off. The dropoffs were sharp, showing the Cannon was working quickly.<\/p>\n\n\n\n<p>I averaged over the six test days to find out how long it took the Cannon to clean the air on average.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/shanghaitestspeed.png\" alt=\"\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-6198f386 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>On average, the Cannon cut .5 micron particulates in half in 10 minutes. By 20 minutes, it removed 80%. <br>Powerful purifiers like the Cannon clean the air very quickly, so I see no need to run the purifier while I&#8217;m not at home.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/do-you-have-to-run-your-purifier-all-day\/\">READ THE FULL ARTICLE HERE \u00bb<\/a> <\/p>\n\n\n\n<div class=\"gb-headline gb-headline-22fa4e96 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-d83fda8f gb-headline-text\" id=\"1.7\">Can I turn it off while I sleep?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">I don&#8217;t recommend it.<\/h5>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/shanghaitesttime.png\" alt=\"\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>The same data from the <a href=\"https:\/\/smartairfilters.com\/en\/blog\/do-you-have-to-run-your-purifier-all-day\/\">&#8220;Do I have to run it all day&#8221; test<\/a> can also answer another question a few people have asked me: &#8220;I don&#8217;t want to hear the fan while I sleep, so can I run it for an hour and then turn it off while I sleep?<\/p>\n\n\n\n<p>In the tests, the air got dirty very quickly after the Cannon turned off (even though the windows and doors were closed). Dirty air is entering our homes constantly, even though we can&#8217;t see it.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-51f9cd67 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>I do <strong><span style=\"text-decoration: underline\">NOT<\/span><\/strong> recommend turning the purifier off while you sleep.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/do-you-have-to-run-your-purifier-all-day\/#:~:text=Can%20I%20turn%20it%20off%20while%20I%20sleep?\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-81458507 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-6b439072 gb-headline-text\" id=\"1.8\">How loud is it?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Original: 52dB. Cannon: 56db.<\/h5>\n\n\n\n<p>The Cannon kicks butt (<a href=\"http:\/\/particlecounting.tumblr.com\/post\/67515725113\/harder-better-faster-stronger-diy\">scientific definition of kicking butt<\/a>), but it&#8217;s noisier than the Original DIY. How noisy is it? As is my habit, I wanted to answer this question scientifically.<\/p>\n\n\n\n<p>So I bought a decibel meter:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/33.media.tumblr.com\/8fb55381fd6aed8432c4592c7fe48c71\/tumblr_inline_nksy387pAC1s4lgm1.png\" alt=\"image\" style=\"width:200px\"\/><\/figure><\/div>\n\n\n<p>And I tested the Cannon, Original DIY, Blue Air 203\/270E, and IQ Health Pro Plus on their highest settings from 1.95 meters away. Here are the results:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/noisecomparison.png\" alt=\"\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>The cannon is noisier than I&#8217;d like, but it&#8217;s similar to the Blue Air on the high setting. To give you an idea of how loud that is, <a href=\"http:\/\/www.industrialnoisecontrol.com\/comparative-noise-examples.htm\">this decibel chart<\/a> says that&#8217;s between &#8220;conversation at home&#8221; and &#8220;conversation in restaurant.&#8221;<\/p>\n\n\n\n<p>It&#8217;s still louder than I&#8217;d like, but fortunately I&#8217;ve found that the Cannon is still very effective on the lower settings:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/cannonsettings.png\" alt=\"\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>So I recommend running the cannon on a lower setting if you find it noisy.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-c26cbce7 gb-headline-text\">Conclusions:<\/h5>\n\n\n\n<p>1. Cannon-owners can use the lower settings without sacrificing much performance.<br>2. For people who are particularly sensitive to noise, the Original may be a better choice.<br>3. For people who are VERY sensitive to noise, the <a href=\"http:\/\/www.p4c.philips.com\/cgi-bin\/dcbint\/cpindex.pl?ctn=AC4072\/00&amp;scy=cn&amp;slg=en\">Philips AC4072<\/a> is expensive (2,700 RMB), but it&#8217;s quite quiet on the low setting.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/china-english-noise\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-f5d74726 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-3dc5e1c6 gb-headline-text\" id=\"1.9\">Why can&#8217;t I just order the filters and fans myself?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">You can! <\/h5>\n\n\n\n<p>We have links in our <a href=\"https:\/\/smartairfilters.com\/en\/blog\/how-to-make-diy-air-purifier\/\">DIY air purifier knowledge base<\/a>. We&#8217;re more committed to spreading the knowledge that HEPA filters are a cheap way to effectively combat air pollution than we are to making money, so we&#8217;d never discourage anyone from buying the same parts elsewhere.<br><br>We just try to make the parts easier to get for people who don&#8217;t want to scour Taobao for the best filters. People have also emailed us saying that some stores stop carrying fans in the winter and that some HEPA manufacturers don\u2019t sell in small orders. We buy in bulk so we can offer a low, flat rate (200RMB) that includes shipping anywhere in Mainland China. By buying with us, you also know that you\u2019re getting HEPAs that we tested personally for effectiveness.<\/p>\n\n\n\n<div class=\"gb-headline gb-headline-780839b6 gb-headline-text\"><a href=\"#using-your-smart-air-purifier\">Return to top<\/a><\/div>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h3 class=\"gb-headline gb-headline-3eee886e gb-headline-text\" id=\"2.1\">How much does outside air affect indoor air?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Strongly.<\/h5>\n\n\n\n<p>I&#8217;ve always wondered: how much does outdoor air pollution affect the air in my home? Even if I keep my windows closed, if the air outside gets really polluted, does air in my home get a lot worse?<\/p>\n\n\n\n<p>To answer that question, my <a href=\"http:\/\/smartairfilters.com\/\">Smart Air<\/a> collaborator Anna took particle counts in her Beijing apartment everyday for two months and compared the counts to outside pollution. Here&#8217;s how she did it:<\/p>\n\n\n\n<p>When she got home from work (and before she turned on her <a href=\"http:\/\/smartairfilters.com\/#diykits\">DIY filter<\/a>), she used a <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">particle counter<\/a> to measure how much particulate matter was in her room and compared it to outside air pollution from the <a href=\"https:\/\/twitter.com\/beijingair\">US Embassy Twitter feed<\/a>. Her windows were always closed, and her home is near Chaoyangmen, which is in central Beijing.<\/p>\n\n\n\n<p>Here&#8217;s the data from 41 days:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/8802e7fecaa49047da8dfba57ab9e811\/tumblr_inline_mve664gj7D1s4lgm1.png\" alt=\"image\"\/><\/figure><\/div>\n\n\n<p>Inside and outside pollution correlate at <em>r <\/em>= .71, which is quite strong. Compare that to <a href=\"http:\/\/particlecounting.tumblr.com\/post\/63023637403\/are-particle-counters-and-government-machines-the-same\">the <\/a><a href=\"http:\/\/particlecounting.tumblr.com\/post\/63023637403\/are-particle-counters-and-government-machines-the-same\"><em>r <\/em><\/a><a href=\"http:\/\/particlecounting.tumblr.com\/post\/63023637403\/are-particle-counters-and-government-machines-the-same\">= .89 correlation between air <strong>outside <\/strong><\/a><a href=\"http:\/\/particlecounting.tumblr.com\/post\/63023637403\/are-particle-counters-and-government-machines-the-same\">my home and the US Embassy numbers<\/a>.<\/p>\n\n\n\n<p>With this data, we can actually start to predict how polluted the air is inside based on how polluted it is outside. To do that, I removed a few outlying datapoints and plotted a regression line:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" src=\"http:\/\/33.media.tumblr.com\/85abb2d14626d27451873126893a77c2\/tumblr_inline_mve6av1wRJ1s4lgm1.png\" alt=\"image\"\/><\/figure><\/div>\n\n\n<p>So when does indoor air pollution get dangerous?<\/p>\n\n\n\n<p>To answer that question, we first have to define &#8220;dangerous.&#8221; I use <a href=\"http:\/\/whqlibdoc.who.int\/hq\/2006\/WHO_SDE_PHE_OEH_06.02_eng.pdf\">the WHO limit<\/a> of concentration of 25 micrograms per meter cubed.<\/p>\n\n\n\n<p>Then we need to convert the PM .5 measurements from my Dylos machine into official concentration numbers. That&#8217;s tough, but we can get a rough estimate based on <a href=\"http:\/\/particlecounting.tumblr.com\/post\/63023637403\/are-particle-counters-and-government-machines-the-same\">my prior tests<\/a>. That data shows that <a href=\"http:\/\/whqlibdoc.who.int\/hq\/2006\/WHO_SDE_PHE_OEH_06.02_eng.pdf\">the WHO limit<\/a> of 25 micrograms is equivalent to about 4,000 on the Dylos. The graph above shows that the air in Anna&#8217;s home is frequently over the WHO pollution limit.<\/p>\n\n\n\n<p>If we round that number up to a more conservative estimate of 5,000, we can reach a rough conclusion: if outside concentration is above 40, the indoor counts are consistently over the 5,000 limit:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/bf767fe490b154833b5ff1da641ada5d\/tumblr_inline_mve8g6YqPi1s4lgm1.png\" alt=\"image\"\/><\/figure><\/div>\n\n\n<p>A concentration of 40 is an AQI of 112. (Remember than governments convert particle concentrations into AQI numbers.) Therefore, we can conclude that, if the AQI is above about 110, the air inside Anna&#8217;s bedroom is more polluted than the WHO limit.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-9063ebb1 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>Outdoor air pollution strongly affects indoor air pollution, and indoor air is often more polluted than the WHO limit \u2014 even with the windows closed.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/china-english-how-much-does-outside-air-pollution-affect-indoor-air\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-f08105c5 gb-headline-text\"><a href=\"#air-pollution-in-china\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-a43312ab gb-headline-text\" id=\"2.2\">Is smoking worse than outdoor air pollution?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>A while back, I posted data I collected from places around Beijing showing that <a href=\"http:\/\/particlecounting.tumblr.com\/post\/58398079343\/how-safe-is-indoor-air\">indoor air is consistently cleaner than outdoor air<\/a>. When I analyzed that data, I excluded places that allow smoking, but I&#8217;m posting the data here now:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/smokingvsoutside.png\" alt=\"image\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>Even on days where outside air was bad (AQI ~ 180), the air was even worse in the cafes that allow smoking. This is even more surprising because:<\/p>\n\n\n\n<p>1. I was not sitting in the smoking section.<\/p>\n\n\n\n<p>2. The smoke was not very noticeable. (The air seemed good enough to me that I sat there and worked \u2014 and I hate smoking.)<\/p>\n\n\n\n<p>My guess is things are much worse in smoky bars and clubs, where the smoke is so thick my clothes smell like smoke the next day.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-94362575 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>Indoor air is better than outdoor air in China, but you lose any advantage once people start smoking \u2014 even if you&#8217;re in the non-smoking section.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/china-english-smoking-is-worse-than-outdoor-air-pollution\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-5617a4a8 gb-headline-text\"><a href=\"#air-pollution-in-china\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-88f2632c gb-headline-text\" id=\"2.3\">Is air pollution just a Beijing problem?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">No!<\/h5>\n\n\n\n<p>Beijing&#8217;s air pollution is the most famous in China, but that can make people in some other cities think their air is good \u2014 at least, not as bad as Beijing&#8217;s. But is the air in other cities safe?<\/p>\n\n\n\n<p>In 2013, Shanghai had newsworthy air pollution that convinced many people in Shanghai that air pollution was a problem there too. But what about Guangzhou? Guangzhou doesn&#8217;t have winter heating. Does that mean its air is safe?<\/p>\n\n\n\n<p>To answer this question, I analyzed all of the <a href=\"http:\/\/www.stateair.net\/web\/post\/1\/3.html\">hourly data from 2014 from the American consulate in Guangzhou<\/a>. Year to date, that data covers 4,572 datapoints. Then I calculated what percentage of those had PM2.5 readings about <a href=\"http:\/\/www.who.int\/mediacentre\/factsheets\/fs313\/en\/\">the WHO 24-hour upper limit of 25 micrograms<\/a> (which is about 77 on the US AQI scale).<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/guangzhouhourly.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>To date, 76.9% of the readings exceeded the WHO upper limit. The average reading was 53.4 micrograms \u2014 over two times the WHO limit.<\/p>\n\n\n\n<p>Breathe safe, Guangzhou!<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/is-guangzhous-air-safe\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-c5060779 gb-headline-text\"><a href=\"#air-pollution-in-china\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-b6c08e7e gb-headline-text\" id=\"2.4\">How does air pollution change throughout the day?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Usually lowest in the afternoon, highest at night.<\/h5>\n\n\n\n<p>My intuition has always been that air pollution is lowest at night because there are fewer cars on the road and fewer factories humming. Apparently I&#8217;m not alone: 139 voted for their guess about what time of day has the lowest PM2.5, and night time came in first:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/timeofdaypoll.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>I also know people who arrange their schedules to work out in the morning to avoid the worst pollution. But how accurate are our intuitions?<\/p>\n\n\n\n<p>To get to the bottom of it, I analyzed thousands of hours of PM2.5 data from the US Embassy in Beijing. When I finally got the answer, I was surprised:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/beijingtimeofday.png\" alt=\"\" style=\"width:450px\"\/><\/figure><\/div>\n\n\n<p>Instead of during the quiet of night, it&#8217;s the afternoon \u2014 right around rush hour \u2014 that PM2.5 is the lowest. So if you&#8217;re planning a picnic or insist on exercising outside, you&#8217;re usually best off between noon and 6pm.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-37f73e61 gb-headline-text\">What about other cities?<\/h5>\n\n\n\n<p>Is that how PM2.5 generally works, or is it unique to Beijing&#8217;s activity or climate? Fortunately, US consulates in several other cities publish their historical data. Find out the air quality levels of four other cities in China <a href=\"https:\/\/smartairfilters.com\/en\/blog\/when-is-pm-2-5-the-lowest\/#:~:text=What%20about%20other%20cities?\">here<\/a>.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-397e8a8a gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p><strong>What time of day is it safest to be outside?<\/strong> In all five cities, the afternoon had the lowest PM2.5 levels. And in contrast to many people&#8217;s intuition, the night time had the worst air in several cities. Thus, you&#8217;re usually best off organizing your picnic or tai chi in the afternoon.<\/p>\n\n\n\n<p>But keep in mind that the air is NEVER safe on average in any of the five cities at any time of day. So take &#8220;safest&#8221; with a grain of salt!<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/when-is-pm-2-5-the-lowest\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-460b936d gb-headline-text\"><a href=\"#air-pollution-in-china\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-f1dbcf6e gb-headline-text\" id=\"2.5\">Does Chinese New Year affect inside air quality?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>I&#8217;ve posted data <a href=\"http:\/\/particlecounting.tumblr.com\/post\/65388796704\/how-much-does-outside-air-pollution-affect-indoor-air\">before<\/a> showing that outdoor air quality is strongly correlated with indoor particle counts (<em>r<\/em> = .71), but Chinese New Year gives nerds like me a great chance to see what happens when we get a momentary shock to air quality.<\/p>\n\n\n\n<p>The media <a href=\"http:\/\/www.npr.org\/blogs\/parallels\/2014\/01\/31\/269216938\/air-quality-worries-dampen-chinese-new-year-fireworks\">made a big deal about<\/a> people cutting back on fireworks this year out of a concern for air quality, and that may be true, but you can still see a strong spike in PM2.5 as Beijingers rang in the year of the horse:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/b7c9db558f267db52af3fe8104df66a9\/tumblr_inline_n0aogaiBPQ1s4lgm1.png\" alt=\"\" style=\"width:450px\"\/><\/figure><\/div>\n\n\n<p>Not all that surprising. But what&#8217;s more interesting is that you can see a corresponding increase in the particle counts in my collaborator Gus&#8217;s bedroom:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/33.media.tumblr.com\/da0d625d297d54aefc2c65eb63a69036\/tumblr_inline_n0aohqrGuP1s4lgm1.png\" alt=\"\" style=\"width:450px\"\/><\/figure><\/div>\n\n\n<p>These indoor counts are without a purifier running, so they demonstrate how quickly outdoor air pollution can find its way indoors and how variable indoor air quality can be in a single room over time. Simply put: the worse the air is outside, the worse it is inside.<\/p>\n\n\n\n<p>A couple of notes for fellow nerds:<\/p>\n\n\n\n<p>1. The indoor particle counts are not precisely on the hours, so the apparent time lag between indoor and outdoor counts may be exaggerated.<\/p>\n\n\n\n<p>2. The early spike in indoor 2.5 micron particles may be because people were moving around the house at that time, which affects the larger 2.5 microns more than the smaller .5.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/do-fireworks-pollute-indoor-air\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-5c10d510 gb-headline-text\"><a href=\"#air-pollution-in-china\">Return to top<\/a><\/div>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h3 class=\"gb-headline gb-headline-e7df22c3 gb-headline-text\" id=\"3.1\">What happens to a room with no purifier in it?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Not much.<\/h5>\n\n\n\n<p>I usually test air purifiers by taking a baseline measurement of particulate pollution in a room, and then turning on the purifier and testing whether the counts drop. My collaborator Gus once suggested another method: run one particle counter in the bedroom that has the purifier, and run another particle counter in a different room that does NOT have a purifier. The benefit of this method is that the control room represents the counterfactual \u2014 what <strong>would have <\/strong>happened if we hadn&#8217;t turned on the air purifier.<\/p>\n\n\n\n<p>Thus, if a northwest wind hits Beijing and makes the outdoor air a lot cleaner, we can separate the effect of the outdoor air fluctuations from the effect of the purifier. In that situation, my old method would artificially raise our estimates of effectiveness. Changes in outdoor air can also artificially lower our estimates of effectiveness if the outdoor air gets dirtier after we turn on the purifier.<\/p>\n\n\n\n<p>In previous tests, I corrected for this by averaging over multiple tests. I also analyzed the data after removing days in which outdoor air pollution fluctuated a lot (for example, I do that sort of analysis <a href=\"http:\/\/particlecounting.tumblr.com\/post\/69541283311\/finally-directly-comparable-tests-diy-versus-blue-air\">in the extra nerd notes here<\/a>).<\/p>\n\n\n\n<p>But it&#8217;s always nice to use different types of tests to make sure an effect is real, so Gus did this experiment. He set up one particle counter in his room and one in his kitchen:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/gusroommap.png\" alt=\"image\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>He let the particle counters run for several hours, and then a timer turned on <a href=\"http:\/\/smartairfilters.com\/#compare\">the Original DIY<\/a> in his room. (The kitchen had no air purifier.) Here&#8217;s what happened:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/twoparticlecounters1.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>The difference between the bedroom and the kitchen air quality can approximate the effect of the air purifier. It looks like Gus would have been breathing 16,000 .5 micron air in his bedroom if he hadn&#8217;t turned on his DIY purifier.<\/p>\n\n\n\n<p>And it&#8217;s pretty clear that the kitchen air quality (where we don&#8217;t have a purifier running) is following outdoor air quality:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/twoparticlecounters2.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>(Be aware that I&#8217;m overlaying these two lines on the same graph, but the Y-axes are different. This is NOT saying that indoor air is as bad as outdoor air. <a href=\"http:\/\/particlecounting.tumblr.com\/post\/58398079343\/how-safe-is-indoor-air\">Indoor air is usually cleaner than outdoor air<\/a>.)<\/p>\n\n\n\n<p><strong>Conclusion: <\/strong>Similar to <a href=\"http:\/\/particlecounting.tumblr.com\/post\/69541283311\/finally-directly-comparable-tests-diy-versus-blue-air\">earlier tests<\/a>, the double particle counter test shows that the DIY purifier is removing particulate pollution from the air.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/a-new-way-to-test-whether-the-diy-works\/#:~:text=The%20Control%20Room%20Purifier%20Test\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-b7c3dec2 gb-headline-text\"><a href=\"#tests-and-comparison\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-e72f21cd gb-headline-text\" id=\"3.2\">Has anyone else tested the DIY purifier?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>Beijing-based Dr. Saint Cyr&#8217;s <a href=\"http:\/\/www.myhealthbeijing.com\/china-public-health\/blueair-vs-iqair-and-the-winner-is\/\">tests of air purifiers<\/a> were one of my original inspirations for the whole DIY project, so I was happy when the DIY became a part of those tests:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><a href=\"http:\/\/www.myhealthbeijing.com\/pollution\/a-200-rmb-diy-air-purifier\/\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/saintcyrtests.png\" alt=\"image\" style=\"width:700px\"\/><\/a><\/figure><\/div>\n\n\n<p>These are the first independent tests of the DIY, and the results parallel mine. You could also include the tests by doctors at the University of Michigan as independent <a href=\"http:\/\/particlecounting.tumblr.com\/post\/56577062878\/independent-confirmation-ive-always-suspected\">&#8220;proof of principle,&#8221;<\/a> although they used a different fan and filter. The commonality is that all of the tests have shown that a simple filter and a fan can reduce particulate pollution in the home.<\/p>\n\n\n\n<p>Dr. Saint Cyr&#8217;s review isn&#8217;t all glowing. He rightly notes that the cannon is noisy, which I&#8217;ve also written about (<a href=\"http:\/\/particlecounting.tumblr.com\/post\/70242116739\/noise\">decibel counts and comparisons here<\/a>). <a href=\"http:\/\/particlecounting.tumblr.com\/post\/70242116739\/noise\">Tests show the cannon is still very effective on the lower settings<\/a>, so I recommend running the cannon on the somewhat quieter settings. And for people who are sensitive to noise, I recommend the quieter Original.<\/p>\n\n\n\n<div class=\"gb-headline gb-headline-c09066d6 gb-headline-text\"><a href=\"#tests-and-comparison\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-e1e27b35 gb-headline-text\" id=\"3.3\">Are all DIY purifiers the same?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">No.<\/h5>\n\n\n\n<p>When I did my first experiments, several people told me not to publish the data. &#8220;Don&#8217;t give it away for free,&#8221; they told me. &#8220;Use it to make money!&#8221;<\/p>\n\n\n\n<p>I decided then that my main goal wasn&#8217;t to make money. I almost got tricked into paying $1,000 for clean air, and I wanted to help people avoid getting tricked too, so I published the data anyway.<\/p>\n\n\n\n<p>Of course, publishing the <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55483627230\/how-to-make-a-diy-air-purifier\">instructions<\/a> online has made it easy for people to copy the idea. \u8fd8\u6211\u84dd\u5929 (<em>Huanwo Lantian<\/em>) was one of the first to follow in our <a href=\"http:\/\/smartairfilters.com\/\">footsteps<\/a>, selling a DIY filter a few months back. They even use a screen capture of Gus&#8217;s appearance on Chinese TV on their shop:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hwltscreencap.png\" alt=\"image\" style=\"width:600px\"\/><\/figure><\/div>\n\n\n<p>I was curious to see how their filter works, so I decided to order one off of Taobao and put it to the test.<\/p>\n\n\n\n<p>Now I&#8217;m in an awkward position because I found that their HEPA was not working nearly as well as my Smart Air HEPAs. It&#8217;s awkward because, if I publish the data, will people think I&#8217;m just trying to attack a competitor?<\/p>\n\n\n\n<p>In the end, I think it&#8217;s better to publish the results and be honest about my conflict of interest. At the very least, I think people have an interest in knowing how well other DIYs work \u2014 especially when some of those websites use graphs that are lifted from my site, which can mislead people into thinking the test results are from their machines.<\/p>\n\n\n\n<p>And as always, I&#8217;m publishing my raw data and testing methods at the end of this post, so fellow nerds can replicate my studies.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-e6145c67 gb-headline-text\">Method<\/h5>\n\n\n\n<p>My collaborator Anna used the same methods as <a href=\"http:\/\/particlecounting.tumblr.com\/post\/69541283311\/finally-directly-comparable-tests-diy-versus-blue-air\">our earlier tests<\/a> in her 15m2 room. Anna did five overnight tests with the same <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">Dylos Pro particle counter<\/a>, and I calculated effectiveness as the percent reduction of particles in the room air, averaging the last three hours (<a href=\"http:\/\/particlecounting.tumblr.com\/post\/69541283311\/finally-directly-comparable-tests-diy-versus-blue-air\">more info<\/a>). Then I compared the results to <a href=\"http:\/\/particlecounting.tumblr.com\/post\/69541283311\/finally-directly-comparable-tests-diy-versus-blue-air\">my earlier tests in the same room<\/a>.<\/p>\n\n\n\n<p>Here&#8217;s what I found:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hwltcomparison.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-8261a2b1 gb-headline-text\">Result<\/h5>\n\n\n\n<p>The \u8fd8\u6211\u84dd\u5929 DIY removed 21% fewer particles .5 microns and above and 11% less 2.5 micron particles than the Original.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-f29248e2 gb-headline-text\">Is it the fan?<\/h5>\n\n\n\n<p>The \u8fd8\u6211\u84dd\u5929 fan is slightly smaller than the <a href=\"http:\/\/smartairfilters.com\/\">Smart Air Original<\/a>, so one explanation could be that the \u8fd8\u6211\u84dd\u5929 fan is just moving less air. Anna tested that by strapping the \u8fd8\u6211\u84dd\u5929 HEPA onto our Original fan.<\/p>\n\n\n\n<p>Here&#8217;s what I found:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hwlthepa.png\" alt=\"image\" style=\"width:350px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-207f0c59 gb-headline-text\">Result<\/h5>\n\n\n\n<p>There wasn&#8217;t much difference. With the new fan, it was getting 4% more PM .5 and 2% less PM2.5. Thus, the fan doesn&#8217;t seem to be the reason.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-d958e0f1 gb-headline-text\">Is it the HEPA?<\/h5>\n\n\n\n<p>The second possibility is that the \u8fd8\u6211\u84dd\u5929 HEPA isn&#8217;t as good. Anna tested the HEPA by doing <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55491154130\/heres-test-1-is-the-air-thats-coming-out-of-the\">air outlet tests<\/a> with a <a href=\"http:\/\/www.metone.com\/particulate-gt521.php\">Met One GT-521<\/a>, which measures down to .3 microns. Anna tested the air coming out of the HEPA for 10 seconds, and I averaged the results from three tests. (More details at the end of the post.)<\/p>\n\n\n\n<p>Here&#8217;s what I found:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hwltpoint3.png\" alt=\"image\" style=\"width:300px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-b429f989 gb-headline-text\">Result<\/h5>\n\n\n\n<p>The \u8fd8\u6211\u84dd\u5929 HEPA performed worse, about 7% lower than the HEPA standard. The major source of the \u8fd8\u6211\u84dd\u5929&#8217;s poor performance seems to be the quality of the filter.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-e6a8efc9 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>In room tests, the \u8fd8\u6211\u84dd\u5929 DIY removes about 21% fewer particles than the <a href=\"http:\/\/smartairfilters.com\/\">Original DIY<\/a>, and the data suggests that the reason is that \u8fd8\u6211\u84dd\u5929 HEPA is lower quality.<\/p>\n\n\n\n<p>Now, don&#8217;t get me wrong. The \u8fd8\u6211\u84dd\u5929 DIY is making the room air cleaner. I&#8217;d rather have a \u8fd8\u6211\u84dd\u5929 than nothing. But the results show that this DIY copycat is cutting corners by using cheap HEPAs.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/are-all-diys-the-same-poor-results-from-huanwolantian\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-911b6c41 gb-headline-text\"><a href=\"#tests-and-comparison\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-8f808d2c gb-headline-text\" id=\"3.4\">Are DIY purifiers still cheap in the long run?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>When I published <a href=\"http:\/\/particlecounting.tumblr.com\/post\/98424809631\/new-tests-can-a-450-rmb-diy-remove-as-much\">tests of the DIY compared to the expensive machines<\/a>, a couple people on <a href=\"http:\/\/zhihu.com\/\">Zhihu<\/a> (China&#8217;s <a href=\"http:\/\/www.quora.com\/\">Quora<\/a>) asked if you really save money in the long run with the DIY once you calculate in the cost of changing the HEPA. After all, the IQ Air HEPA costs 1,782 RMB, but you can use it for more than a year.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-250d4334 gb-headline-text\">Long-Term DIY HEPA Costs<\/h5>\n\n\n\n<p>At that time I didn&#8217;t have an answer. To get an honest answer, I needed to do tests in the real world, but that took almost a year to complete. (That&#8217;s more than I can say for the numbers IQ Air and Blue Air give. If filters last 6 months in Sweden, are they going to last 6 months in Beijing?)<\/p>\n\n\n\n<p>Now it&#8217;s a year later, and I have that data. <a href=\"http:\/\/smartairfilters.com\/\">Smart Air<\/a> co-founder <a href=\"http:\/\/smartairfilters.com\/en#about\">Gus<\/a> ran his <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7525708604.3.kAVOPv&amp;id=35171288192\">Original DIY<\/a> for eight hours a day and tracked what percentage of particulate it removed from the air each day with a Dylos particle counter.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/longevityaverage.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>Based on that data, I recommend changing HEPAs after 140 days at 8 hours per day (about 1,000 hours of use). Since that HEPA costs <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7525708604.7.oZL7Uk&amp;id=35110622876\">80 RMB<\/a>, that averages to .57 RMB per day and 208.6 RMB per year.<\/p>\n\n\n\n<p>To get an idea of what that means, we can compare that to the cost of drinking a bottle of water a day:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hepaoneyearcost.png\" alt=\"image\" style=\"width:300px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-a00ad1ba gb-headline-text\">Big Brand HEPA Costs<\/h5>\n\n\n\n<p>I&#8217;m highly skeptical that HEPA recommendations for Sweden can be mapped onto China. But to be conservative, I&#8217;ll assume in my calculations that their numbers work the same in China.<\/p>\n\n\n\n<p>I calculated costs for the Blue Air 203 and IQ Air Health Pro Plus using the same conditions I used for the <a href=\"http:\/\/particlecounting.tumblr.com\/post\/103916187666\/hepa-longevity-test-day-200\">Original DIY longevity test<\/a>:<\/p>\n\n\n\n<p>A. Highest setting<br>B. 8 hours of use per day<br>C. Extend those costs over a year<br>D. Include the cost of pre-filters but not carbon filters<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-901519b8 gb-headline-text\">Blue Air<\/h5>\n\n\n\n<p>Blue Air&#8217;s HEPA costs <a href=\"http:\/\/www.amazon.com\/Blueair-Series-Particle-Replacement-Filter\/dp\/B000E7B4KO\/ref=pd_sim_hg_1?ie=UTF8&amp;refRID=18E0636KGGGWF9KRRTP0\">300 RMB<\/a> and lasts 6 months. That works out to 1.67 RMB per day and 609.6 RMB per year.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hepaoneyearcostblueair.png\" alt=\"image\" style=\"width:320px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-d0d9ee3b gb-headline-text\">IQ Air<\/h5>\n\n\n\n<p>IQ Air&#8217;s HEPA is more expensive: <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a230r.1.0.0.CS0NLM&amp;id=38490711315&amp;ns=1&amp;abbucket=9#detail\">1,782 RMB<\/a>. On the sixth setting, it lasts 4,968 hours. If you use it 8 hours a day, that works out to 2.87 RMB per day and 1,047.4 RMB per year.<\/p>\n\n\n\n<p>However, we have to add the cost of the pre-filter because the HEPA lifespan depends on the pre-filter. The pre-filter costs <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a230r.1.14.36.SR7wf9&amp;id=37532591265&amp;ns=1&amp;abbucket=20#detail\">645 RMB<\/a> and lasts 2,016 hours on the sixth setting. That works out to 2.56 RMB per day and 934.3 RMB per year.<\/p>\n\n\n\n<p>IQ Air grand total: 1,982 RMB per year.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/hepaoneyearcostiqair.png\" alt=\"image\" style=\"width:320px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-a5093f58 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>The long-term HEPA cost for the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7525708604.3.MFH0wU&amp;id=35171288192\">Original DIY<\/a> is 66-89% less than the Blue Air and IQ Air.<br>It should be noted that these results may not map onto the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7525708604.1.qpI0ol&amp;id=36350325474\">Cannon<\/a>. I&#8217;m still working on the Cannon longevity test, so we&#8217;ll need to wait until that test is done.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/are-diy-purifiers-still-cheap-in-the-long-run\/\">READ THE FULL ARTICLE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-519e7b5d gb-headline-text\"><a href=\"#tests-and-comparison\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-904fd877 gb-headline-text\" id=\"3.5\">Are cheaper HEPAs possible?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes, but at a cost.<\/h5>\n\n\n\n<p>After I published <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55483627230\/how-to-make-a-diy-air-purifier\">directions for how to make your own purifier<\/a>, people asked me: &#8220;Which HEPAs should I use? Is this one trustworthy?&#8221;<\/p>\n\n\n\n<p>That&#8217;s the type of question that makes a nerd like me happy because it means we need to get more data. So I ordered HEPAs from every manufacturer I could find, and I tested them all. After all the testing was done, I found I could ship the HEPAs that worked best for 80 RMB, which was cheaper than <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55483627230\/how-to-make-a-diy-air-purifier\">the 110 RMB HEPAs I was buying<\/a> \u2014 quality and price!<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-5c311a02 gb-headline-text\">Can HEPAs be even Cheaper?<\/h5>\n\n\n\n<p>Later I found HEPAs for 20 RMB wholesale. I was excited. If HEPAs are that cheap, we can make the DIY even cheaper!<\/p>\n\n\n\n<p>But the test data was terrible. These HEPAs weren&#8217;t anywhere close to getting 99% of particles, so I passed on them. If didn&#8217;t want to use it in my home, why would I want to ship them to other people?<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-e4e5d98b gb-headline-text\">A 99.97% HEPA for 30 RMB?<\/h5>\n\n\n\n<p>Thus I wasn&#8217;t surprised a couple weeks ago when I saw a store on Taobao selling HEPAs for 30 RMB and claiming that my HEPAs are \u66b4\u529b (aggressively overpriced). They claim that their HEPAs get 99.97% of particles, and if that&#8217;s true, maybe these were the holy grail of HEPAs I was looking for all along!<\/p>\n\n\n\n<p>So I ordered two online and put them to the test. The first shock was seeing that it doesn&#8217;t have a frame:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/33.media.tumblr.com\/2b9259e763698643bb56bf381269fd0f\/tumblr_inline_nie5o5mMTD1s4lgm1.png\" alt=\"image\" style=\"width:200px\"\/><\/figure><\/div>\n\n\n<p>That makes it harder retain its shape, but it might still be effective without a frame, so I put it through the tests.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-f0aafffa gb-headline-text\">Air Outlet Test<\/h5>\n\n\n\n<p>First, I tested it by putting it on <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7525708604.1.hLb0D0&amp;id=36350325474\">the Cannon<\/a> and testing the air coming out of the HEPA with a <a href=\"http:\/\/www.metone.com\/particulate-aero531.php\">Met One Aerocet 531S<\/a>. (The Met One is useful because it has a pump to regulate airflow. In air outlet tests, the particle counter is sitting in a stream of air, so using a pump maintains constant readings.)<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/baixingoutlet.png\" alt=\"image\" style=\"width:320px\"\/><\/figure><\/div>\n\n\n<p>The results weren&#8217;t pretty. Smart Air HEPAs got over 99.9% of particles, but the 30 RMB HEPA was below 90% \u2014 far below their claim of 99.97%.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-578c1f47 gb-headline-text\">Air Speed<\/h5>\n\n\n\n<p>But particle effectiveness isn&#8217;t everything. A HEPA in the 80% range <strong>might<\/strong> work better if it has better air flow. In that case, maybe the HEPA could process the air more times and clean the room air as well as a real HEPA.<\/p>\n\n\n\n<p>To test that possibility, I put each HEPA on the Cannon and used a tool to measure air speed (fancy name &#8220;<a href=\"http:\/\/en.wikipedia.org\/wiki\/Anemometer\">anemometer<\/a>&#8220;). I placed the anemometer on the HEPA at four locations (left, right, top, bottom) and took the average air speed.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/baixingspeed.png\" alt=\"image\" style=\"width:320px\"\/><\/figure><\/div>\n\n\n<p>Again, the results weren&#8217;t pretty. So not only was the 30 RMB HEPA getting far fewer particles, it was letting much less air through.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-b262481d gb-headline-text\">Conclusion<\/h5>\n\n\n\n<p>Quality HEPAs for 30 RMB are still a dream. They&#8217;re not useless, but using this 30 RMB HEPA would expose people to significantly more particles.<\/p>\n\n\n\n<p>I still hold out hope that manufacturers will be able to innovate cheaper HEPAs without sacrificing quality, but I haven&#8217;t seen those HEPAs yet.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-886fb147 gb-headline-text\">Is the Taobao Store Owner Being Dishonest?<\/h5>\n\n\n\n<p>The 30 RMB HEPA store makes claims that their HEPAs get 99.97% of particles, and the data clearly contradicts that, so it&#8217;s tempting to think that they&#8217;re lying.<\/p>\n\n\n\n<p>But are they? I don&#8217;t know what&#8217;s in their mind, but my guess is that they simply didn&#8217;t go through the hassle of buying a particle counter and testing the HEPAs. I suspect that half of what seems like dishonesty on Taobao is actually just sloppiness.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/is-a-30rmb-hepa-reliable\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-4b8b0abd gb-headline-text\"><a href=\"#tests-and-comparison\">Return to top<\/a><\/div>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h3 class=\"gb-headline gb-headline-133f3743 gb-headline-text\" id=\"4.1\">Does carbon really work?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p>HEPAs do an amazing job at removing particulates, but particulates aren&#8217;t everything. Gases like <a href=\"http:\/\/www.epa.gov\/iaq\/voc.html\">volatile organic compounds<\/a> (VOCs) are so small that they slip through HEPAs. &#8220;VOC&#8221; is a big category, including things like benzene and formaldehyde. <a href=\"http:\/\/www.epa.gov\/iaq\/voc.html\">VOCs can cause cancer, throat irritation, dizziness, and other not-fun side effects<\/a>.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/33.media.tumblr.com\/4c3f1e8d09f2b9a1dfdb00bfafaf8fe1\/tumblr_inline_ngupi8TKBY1s4lgm1.png\" alt=\"image\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>And for homes that have VOCs problems, we&#8217;re supposed to use activated carbon filters. But do they actually work?<\/p>\n\n\n\n<p>When I published <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55483627230\/how-to-make-a-diy-air-purifier\">the instructions for how to build your own purifier<\/a>, I wasn&#8217;t comfortable recommending activated carbon because I hadn&#8217;t tested it, and I didn&#8217;t want to just trust what the big filter companies say. So this year, I set out on a journey to test whether carbon actually works.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-f3108de9 gb-headline-text\">Method<\/h5>\n\n\n\n<p>I soon learned that gas testing is not easy. First off, &#8220;harmful gases&#8221; is not a natural category. You can buy a particle counter that will detect all particles of a certain size, but there is no detector that will detect all gases. Instead, you need one for each type of gas, and that is not cheap.<\/p>\n\n\n\n<p>In this case, my scientific curiosity cost me $3,542 for this <a href=\"http:\/\/www.indsci.com\/products\/multi-gas-detectors\/mx6\/\">Industrial Scientific Ibrid MX6<\/a>. It detects VOCs, carbon monoxide, sulfur dioxide, hydrogen sulfide, and nitrogen dioxide. It uses a <a href=\"http:\/\/en.wikipedia.org\/wiki\/Photoionization_detector\">photo-ionization detector<\/a> to measure VOCs from 0-2,000 parts per million with a resolution of .1.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/104b82bd2c888dc7de690eecb274e9e3\/tumblr_inline_ngg3njKnyS1s4lgm1.png\" alt=\"image\" style=\"width:150px\"\/><\/figure><\/div>\n\n\n<p>Next, I needed a source of gas pollution. Interestingly enough, my apartment didn&#8217;t have enough VOCs to register on the MX6 \u2014 nor did 8 other Beijing apartments I tested. (That speaks to whether purifier companies should scare people into thinking that everyone needs carbon.)<\/p>\n\n\n\n<p>Because I didn&#8217;t have detectable VOCs in my home, I had to go out and find VOCs to pump into my room. I chose cigarettes because they are <a href=\"http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/18351112\">known to emit VOCs like benzene<\/a> and <a href=\"http:\/\/www.cancerresearchuk.org\/cancer-info\/healthyliving\/smoking-and-cancer\/whats-in-a-cigarette\/smoking-and-cancer-whats-in-a-cigarette\">formaldehyde<\/a>.<\/p>\n\n\n\n<p>In each test, I burned 3 Marlboro cigarettes in an enclosed 3.78 m2 porch. At the same time, I ran <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7525708604.2.ymMhps&amp;id=36350325474\">the Cannon<\/a> on high for five tests with a <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7528923369.1.o1kYOk&amp;id=42959087014\">composite carbon filter<\/a> on the front:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7528923369.1.o1kYOk&amp;id=42959087014\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/874721704258973b7c34d4f5166c9ed2\/tumblr_inline_ngg4q3a9Gq1s4lgm1.png\" alt=\"image\" style=\"width:200px\"\/><\/a><\/figure><\/div>\n\n\n<p>I ran four control tests with a fan but no filter. That way the room still has air flow, but no carbon. The cigarettes burned out after about 15 minutes, and I left the fans on for another 30 minutes.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-6f428f9b gb-headline-text\">Results<\/h5>\n\n\n\n<p>Looking at the Cannon + carbon alone after the cigarette extinguished, the VOCs dropped. Here is the data from one test:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/voc1.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>From there we can zoom out to include the time the cigarette was burning and the control fan-only condition. From there, it becomes clearer that the carbon was removing VOCs above and beyond just having a fan on.<\/p>\n\n\n\n<p>Averaging across all of the tests, the VOCs reached a maximum of about 1 ppm while the carbon was on. Without the carbon, VOCs reached 1.5 ppm.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/voc2.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>After the cigarette burned out, the Cannon cleared the air of VOCs in 5 minutes to just over 15 minutes on average. Without carbon, the air still had VOCs after 30 minutes.<\/p>\n\n\n\n<p>Averaging over all of the tests, the carbon removed 38% of VOCs by the time the cigarettes burned out compared to the fan-only condition. The Cannon removed 68% after another 5 minutes and 100% by 20 minutes after the cigarettes burned out.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/voc3.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-41f31e93 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>The results showed that carbon effectively removed VOCs. Thus, I&#8217;ve decided these filters are ready for game time. I&#8217;ve started shipping these tested carbon filters via <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7528923369.1.o1kYOk&amp;id=42959087014\">Taobao<\/a> and <a href=\"http:\/\/smartairfilters.com\/en#diykits\">PayPal<\/a> for 70 RMB.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/does-carbon-really-work\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-f4b40fa4 gb-headline-text\"><a href=\"#gases-and-carbon\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-90ef0e6f gb-headline-text\" id=\"4.2\">Does everyone need carbon?<\/h3>\n\n\n\n<p>Purifier companies have a financial incentive to convince people to buy carbon filters. They make more money if they can scare people into buying carbon. But does everyone need carbon?<\/p>\n\n\n\n<p>I don&#8217;t want to scare people into buying carbon. Why? In most homes, my MX6 detected zero VOCs. I only found VOCs in homes that had an obvious source of pollution such as remodeling or smoke. And in all of the places where the MX6 detected VOCs, I was able to notice a chemical smell. That makes sense, since lots of VOCs have noticeable smells, like <a href=\"http:\/\/en.wikipedia.org\/wiki\/Benzene\">benzene<\/a>, <a href=\"http:\/\/en.wikipedia.org\/wiki\/Toluene\">toluene<\/a>, and <a href=\"http:\/\/en.wikipedia.org\/wiki\/Formaldehyde\">formaldehyde<\/a>.<\/p>\n\n\n\n<p>Now, I don&#8217;t want to say that VOCs are never a problem. Photo ionization detectors like the MX6 are not the most sensitive test type out there. I bet I&#8217;d pick up small amounts of VOCs if I sent air samples to a laboratory.<\/p>\n\n\n\n<p>However, scientists have used fancier methods and found similar results. For example, scientists in Hong Kong tested homes and found that <a href=\"http:\/\/www.sciencedirect.com\/science\/article\/pii\/S1352231001004356\">most non-smoking homes did not have un-safe levels of VOCs<\/a>. We need more tests like this.<\/p>\n\n\n\n<p>For now, I will not be using carbon in my home, but I think it is right for people whose homes have:<\/p>\n\n\n\n<p>1. Recent remodeling<br>2. Recent painting<br>3. Smoking<br>4. Odors<br>5. Nearby sources of gas pollutants (such as living near a factory)<br>6. Symptoms such as inflammation and asthma<\/p>\n\n\n\n<div class=\"gb-headline gb-headline-6c393960 gb-headline-text\"><a href=\"#gases-and-carbon\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-49fba971 gb-headline-text\" id=\"4.3\">Do I still need the HEPA?<\/h3>\n\n\n\n<p>Yes. <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55405181445\/types-of-filters\">Carbon is designed to get organic compounds, not particulate in general<\/a>. I wouldn&#8217;t have even tested this, but <a href=\"http:\/\/smartairfilters.com\/en#about\">Anna<\/a> accidentally forgot to attach the HEPA and unknowingly ran <a href=\"http:\/\/particlecounting.tumblr.com\/post\/98424809631\/new-tests-can-a-450-rmb-diy-remove-as-much\">a regular particulate room test<\/a> with carbon only.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/doistillneedahepa.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>The results weren&#8217;t pretty \u2014 far below the 95% reduction with the added HEPA. Thus, I do not recommend using carbon only.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/does-carbon-really-work\/#:~:text=Do%20I%20Still%20Need%20The%20HEPA?\">READ THE FULL ARTICLE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-46253249 gb-headline-text\"><a href=\"#gases-and-carbon\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-ac257909 gb-headline-text\" id=\"4.4\">Does adding a carbon layer reduce particulate effectiveness?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Not significantly on the Cannon, significantly on the Original.<\/h5>\n\n\n\n<p>I recently published <a href=\"http:\/\/particlecounting.tumblr.com\/post\/105818344169\/does-carbon-really-work\">tests showing that carbon actually removes VOCs<\/a>. But adding that carbon layer raises a question: adding carbon means the fan has to power through yet another layer of resistance. Does that make purifier less effective at removing particulates?<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-54953139 gb-headline-text\">Methods<\/h5>\n\n\n\n<p>To test this question, I ran 10 room tests with <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7525708604.1.wIxSnY&amp;id=36350325474\">the Cannon<\/a> and 10 tests with the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7525708604.3.wIxSnY&amp;id=35171288192\">Original DIY<\/a> in the same 15m2 Beijing apartment as <a href=\"http:\/\/particlecounting.tumblr.com\/post\/67515725113\/harder-better-faster-stronger-diy\">my earlier tests without a carbon layer<\/a>.<\/p>\n\n\n\n<p>I measured how much particulate it removed with a <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">Dylos particle counter<\/a> and compared the particle counts (1) before I turned on the purifier at night and (2) the average of the last four hours before I woke up in the morning.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-360e0827 gb-headline-text\">Results<\/h5>\n\n\n\n<p>With the additional carbon, <a href=\"http:\/\/smartairfilters.com\/en#compare\">the Cannon<\/a> particulate effectiveness dropped 1-2%. Thus carbon has a very minor negative effect on the Cannon.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/carbonparticles.png\" alt=\"\" style=\"width:350px\"\/><\/figure><\/div>\n\n\n<p>However, the <a href=\"http:\/\/smartairfilters.com\/en#compare\">Original DIY<\/a> had a harder time powering through the extra layer. Its 0.5 micron effectiveness dropped 19%, and 2.5 micron effectiveness dropped 15%.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/carbonparticlesoriginal.png\" alt=\"\" style=\"width:320px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-7dabf4aa gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>For people who need carbon (<a href=\"http:\/\/particlecounting.tumblr.com\/post\/105818344169\/does-carbon-really-work\">and that is not everyone<\/a>), I would recommend adding the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1.w4004-7528923369.1.yLT3Pq&amp;id=42959087014\">carbon<\/a> to the Cannon, but I would think twice about adding carbon to the Original.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/does-adding-carbon-reduce-particle-effect\/\">READ THE FULL ARTICLE HERE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-9718e491 gb-headline-text\"><a href=\"#gases-and-carbon\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-72990af1 gb-headline-text\" id=\"4.5\">Can carbon remove formaldehyde?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Yes.<\/h5>\n\n\n\n<p><strong>Why are people in China so concerned with formaldehyde?<\/strong><br>Formaldehyde causes scary health problems like <a href=\"http:\/\/www.epa.gov\/airtoxics\/hlthef\/formalde.html\">ulcers and cancer<\/a>, yet it&#8217;s common in construction materials and new furniture. The people who should worry the most are people in new or recently renovated homes. Tests of new and renovated homes routinely <a href=\"http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/19589601\">find high levels of formaldehyde<\/a>.<\/p>\n\n\n\n<p><strong>Why formaldehyde is so hard to remove?<\/strong><br>Formaldehyde is a tricky problem because it escapes from materials as a gas, and HEPA filters aren&#8217;t made to capture gases. I&#8217;ve heard companies claim that activated carbon can remove formaldehyde, but I&#8217;ve also seen companies selling <a href=\"http:\/\/detail.tmall.com\/item.htm?spm=a230r.1.14.251.LlMGWq&amp;id=39633685785&amp;ns=1&amp;abbucket=20\">sprays that claim to clear formaldehyde from your home<\/a>. That sounds a lot like snake oil to me.<\/p>\n\n\n\n<p>Since there&#8217;s a profit motivation for companies to claim they can get rid of formaldehyde, I wanted to empirically test whether carbon actually works.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-32ee6132 gb-headline-text\">Tests<\/h5>\n\n\n\n<p>In my quest for an answer, the first stumbling block was detecting formaldehyde. Many companies on Taobao will <a href=\"http:\/\/detail.tmall.com\/item.htm?spm=a230r.1.14.38.UZEmQv&amp;id=40450190693&amp;ns=1&amp;abbucket=20\">sell you a &#8220;formaldehyde detector&#8221;<\/a>, but they&#8217;re actually general <a href=\"http:\/\/en.wikipedia.org\/wiki\/Volatile_organic_compound\">VOC<\/a> detectors. (There are lots of volatile organic compounds; formaldehyde is one type.) So even if the machine tells you it&#8217;s detecting formaldehyde, you have no way of knowing whether it&#8217;s formaldehyde or some other VOC.<\/p>\n\n\n\n<p>Thus, to be absolutely sure we were detecting formaldehyde, my collaborator <a href=\"http:\/\/smartairfilters.com\/en#about\">Anna<\/a> bought bottles of liquid formaldehyde \u2014 risking our health for science!<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/40.media.tumblr.com\/07dc3950c98b9aa90bb006a33fd442c8\/tumblr_inline_nnhx0geS9E1s4lgm1_250.png\" alt=\"\" style=\"width:150px\"\/><\/figure><\/div>\n\n\n<p>To spread it in the room, we put it in a rice cooker along with 250 ml of water in a 4.14m2 porch (volume 10.35m3). When the rice cooker heats up, it releases formaldehyde as a gas into the air.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/40.media.tumblr.com\/ebe3c50f49ef5c435c31624e8380ed69\/tumblr_inline_nndgj5Ne8P1s4lgm1_500.jpg\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>The <a href=\"https:\/\/www.indsci.com\/products\/multi-gas-detectors\/mx6\/\">Industrial Scientific MX6<\/a> detects different types of VOCs, not formaldehyde specifically. But because we released formaldehyde in the room, we can be sure that VOC is formaldehyde.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/104b82bd2c888dc7de690eecb274e9e3\/tumblr_inline_nk7bstFV0b1s4lgm1.png\" alt=\"\" style=\"width:150px\"\/><\/figure><\/div>\n\n\n<p>To attack the formaldehyde, Anna put a <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7528923369.1.ZfJxFI&amp;id=42959087014\">composite activated carbon filter<\/a> on the <a href=\"http:\/\/item.taobao.com\/item.htm?spm=a1z10.1-c.w4004-7525708604.1.fUkC7K&amp;id=36350325474\">Cannon<\/a>.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/31.media.tumblr.com\/874721704258973b7c34d4f5166c9ed2\/tumblr_inline_nl0pxnxw8m1s4lgm1.png\" alt=\"\" style=\"width:200px\"\/><\/figure><\/div>\n\n\n<p>Anna turned the cooker and the fan on at the same time and let them run until the VOC level fell back to zero. We also ran a control test with a fan only. We ran a total of three carbon tests and two fan-only tests.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-267248ae gb-headline-text\">Results<\/h5>\n\n\n\n<p>Here&#8217;s what one of the carbon tests looked like, starting from the peak formaldehyde level:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/40.media.tumblr.com\/b91b3f0b9296da5b4d4945ee2c2cc3b2\/tumblr_inline_nnsry0ejTx1s4lgm1_500.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>But we need to be sure that&#8217;s the effect of the carbon, not just the formaldehyde dispersing over time. To do that, we need to compare those results to the fan-only condition. Here&#8217;s what the two tests look like side by side:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/formaldehyde1.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<p>The formaldehyde levels stayed higher for longer in the fan-only condition, but the levels dropped much quicker when we used carbon.<\/p>\n\n\n\n<p>I averaged across all three carbon tests and compared the average reduction compared to the fan-only condition. On average, the carbon reduced formaldehyde levels to 50% within 15 minutes of the peak formaldehyde levels and then down 0% by 25 minutes.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/formaldehyde2.png\" alt=\"\" style=\"width:400px\"\/><\/figure><\/div>\n\n\n<h5 class=\"gb-headline gb-headline-0e933eef gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>These composite activated carbon filters removed formaldehyde from the air. <a href=\"http:\/\/particlecounting.tumblr.com\/post\/105818344169\/does-carbon-really-work\">My earlier tests<\/a> show that these filters remove other types of VOCs too.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/activated-carbon-formaldehyde-filter-remove-vocs\/\">READ THE FULL ARTICLE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-f753bc9a gb-headline-text\"><a href=\"#gases-and-carbon\">Return to top<\/a><\/div>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<h3 class=\"gb-headline gb-headline-023bab86 gb-headline-text\" id=\"5.1\">Does air conditioning bring in dirty outside air?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">No.<\/h5>\n\n\n\n<p>A question that I get asked often (and that I have always wondered about) is whether my wall-mounted air conditioner is bringing in dirty air from outside. If so, it&#8217;d be safer not to use it, especially on really bad days.<\/p>\n\n\n\n<p>My short answer is no. To explain why, I&#8217;ve got three points of evidence:<\/p>\n\n\n\n<p>1. <strong>How air conditioners work.<\/strong> Regular wall-mounted air conditioners in China do have a unit outside connected with tubes to the inside, but that tube is not bringing in outside air. It&#8217;s passing coolant, and letting heat escape outside.<\/p>\n\n\n\n<p>So where does the air it&#8217;s blowing come from? If you look around your air conditioner, you&#8217;ll probably discover that it works like mine: it brings air from the top, runs it over the cooling coils, and blows it out the front. It&#8217;s recycling indoor air, not bringing in outdoor air.<\/p>\n\n\n\n<p>2. <strong>Tests of the air coming out of the air conditioner.<\/strong> (<a href=\"http:\/\/particlecounting.tumblr.com\/post\/59177657783\/is-your-air-conditioner-bringing-in-dirty-outside\">See a live test here<\/a>.) I&#8217;ve held <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">my particle counter<\/a> up into the air coming out of my AC unit, and it&#8217;s no different from the ambient room air. I&#8217;ve also compared that air to outside air on very dirty days, and the air coming out of the AC is nowhere near as dirty as outside air.<\/p>\n\n\n\n<p>(I did this test when I had just turned on my AC. If the AC were bringing in dirty air and I were to test the exhaust after I had been running the AC for a long time, then my whole room would be dirty, not just the exhaust.)<\/p>\n\n\n\n<p>3. <strong>Tests of the ambient room air before and after turning the AC on.<\/strong> Results? AC makes basically no difference. Here are the results of 7 tests I did in my bedroom.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/ac.png\" alt=\"\" style=\"width:450px\"\/><\/figure><\/div>\n\n\n<p>In each test, I ran my particle counter for 30 minutes to get a baseline. Then I turned on the AC for 30 minutes. Here I&#8217;m comparing the numbers just before I turned the AC on and 30 minutes later. As you can see, there&#8217;s basically no effect. If anything, 2.5 micron particles go down slightly. This could be because of the coarse filter in the AC unit. Or it could be random variation.<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-d0aa6570 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>If it&#8217;s hot outside, don&#8217;t sweat it. Use your AC.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/air-conditioner-bring-dirty-outside-air\/\">READ THE FULL ARTICLE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-a72dfb18 gb-headline-text\"><a href=\"#more-faqs\">Return to top<\/a><\/div>\n\n\n\n<h3 class=\"gb-headline gb-headline-37ccbaaf gb-headline-text\" id=\"5.2\">Are our particle counters the same as government air monitors?<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">No.<\/h5>\n\n\n\n<p><a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">My particle counter<\/a> is a beast \u2014 I&#8217;ve loved it. But I&#8217;ve always wondered how the counts of laser particle counters like mine: <\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/f142d0518720b08eed5d148aa3b9b5d6\/tumblr_inline_mu42o7Qhz61s4lgm1.jpg\" alt=\"image\" style=\"width:240px\"\/><\/figure><\/div>\n\n\n<p>\u2026compare to the measurements of the huge stationary air quality monitoring stations that governments use, like this one in New Zealand:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><a href=\"http:\/\/commons.wikimedia.org\/wiki\/File:NSW_EPA_air_quality_monitoring_station.jpg\"><img decoding=\"async\" src=\"http:\/\/38.media.tumblr.com\/59f55463fa6efab19fccaadee7d96ad1\/tumblr_inline_mtuulwmrvp1s4lgm1.jpg\" alt=\"image\" style=\"width:400px\"\/><\/a><\/figure><\/div>\n\n\n<p>If you look at the <a href=\"https:\/\/twitter.com\/beijingair\">US Embassy&#8217;s Twitter feed<\/a>, you&#8217;ll notice that its raw numbers are &#8220;concentration,&#8221; which <a href=\"http:\/\/www.stateair.net\/web\/post\/1\/1.html\">it explains<\/a> are micograms per cubic meter (\u00b5g\/m\u00b3). <a href=\"http:\/\/alg.umbc.edu\/umap\/bam_index.html\">The way government (BAM) machines work<\/a> is that they use a source of carbon 14 that emits beta particles and then measure how many of those beta particles make it through to a detector. They then use those numbers to estimate the <strong>weight<\/strong> of those particles (micrograms).<\/p>\n\n\n\n<p>In contrast, laser particle counters like <a href=\"http:\/\/particlecounting.tumblr.com\/post\/55427024364\/the-beast-the-dylos-dc1100-pro-air-quality\">mine<\/a> use a laser and a photo diode sensor to estimate <strong>the number<\/strong> of particles in the air. I don&#8217;t see why the weight should be any more important than the number \u2014 they&#8217;re both telling you how much particulate pollution is in the air.<\/p>\n\n\n\n<p>As an analogy, if we want to understand the crowd at a basketball game, we could count the number of people, or we could weigh those people. Of course, the more people, the heavier the total weight. And of course the two numbers won&#8217;t correlate perfectly if we have more heavy people on some days and more children on other days. But the weight and the total number should correlate highly.<\/p>\n\n\n\n<p>The other major difference is that laser particle counters give the number of particles at that particle size <strong>and above<\/strong>. Government machines give the number of particles at that size <strong>and below<\/strong>.<\/p>\n\n\n\n<p>To see how the two numbers compare, I put my particle counter outside my second-story window 70 times (that&#8217;s nerd dedication!) and compared my numbers to the US Embassy&#8217;s Twitter feed at the same time. Here&#8217;s what they look like:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/embassy1.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>They correlate at <em>r <\/em>= .89, meaning the two numbers are very strongly related (remember the highest possible correlation is 1). That high correlation is especially impressive given that my house is near Gulou, and the US Embassy is out in Liangmaqiao \u2014 about 7 kilometers away.<\/p>\n\n\n\n<p>The difference between the readings was particularly noticeable on days where a strong wind moved through Beijing. I noticed several times that my particle counts would drop before the embassy&#8217;s counts as the wind moved in from the west (where my house was) to the east (where the embassy is). (Remember, <a href=\"http:\/\/www.livefrombeijing.com\/2013\/01\/seeking-solutions-to-chinas-air-pollution-crisis\/\">Beijing&#8217;s air gets a lot cleaner when we get winds from the west<\/a>.)<\/p>\n\n\n\n<p>If we want to get a rough conversion between the numbers, we can remove a few of the outliers and compute a regression line:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/embassy2.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>For example, a government concentration of 100 micrograms (four times <a href=\"http:\/\/whqlibdoc.who.int\/hq\/2006\/WHO_SDE_PHE_OEH_06.02_eng.pdf\">the WHO limit<\/a>!) is approximately 25,000 on the Dylos particle counter:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter is-resized\"><img decoding=\"async\" src=\"\/images\/datacenterimages\/embassy3.png\" alt=\"image\" style=\"width:500px\"\/><\/figure><\/div>\n\n\n<p>And the 24-hour WHO standard of 25 \u00b5g\/m\u00b3 is about 3,000-4,000 on the Dylos.<\/p>\n\n\n\n<p>During my home tests (before turning my filter on), the air inside my home was very often above 3,000 (even though it was still <a href=\"http:\/\/particlecounting.tumblr.com\/post\/58398079343\/how-safe-is-indoor-air\">much cleaner than outside<\/a>).<\/p>\n\n\n\n<h5 class=\"gb-headline gb-headline-b29ce3a4 gb-headline-text\">Conclusion:<\/h5>\n\n\n\n<p>My particle counter is giving measurements that are highly related to the much larger air monitoring stations. The scale is different, but the two can be roughly converted.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><a href=\"https:\/\/smartairfilters.com\/en\/blog\/are-particle-counters-and-government-machines-the-same\/\">READ THE FULL ARTICLE \u00bb<\/a><\/p>\n\n\n\n<div class=\"gb-headline gb-headline-23018f38 gb-headline-text\"><a href=\"#more-faqs\">Return to top<\/a><\/div>\n\n\n\n<div style=\"height:50px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>","protected":false},"excerpt":{"rendered":"<p>Is the air coming out of the air purifier clean? Yes. This is the easiest question to answer, and we can do it by holding the particle counter in front of the unit and watching the numbers drop. Here&#8217;s a video of me doing just that: (Can&#8217;t see the video? &#8230; <\/p>\n<p class=\"read-more-container\"><a title=\"Air Pollution and Air Purifier Data\" class=\"read-more button\" href=\"https:\/\/smartairfilters.com\/en\/data\/#more-17022\" aria-label=\"Read more about Air Pollution and Air Purifier Data\">Read more<\/a><\/p>\n","protected":false},"author":9575,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"6631,22029,11976,13492,20657,4921","_relevanssi_noindex_reason":"","footnotes":""},"class_list":["post-17022","page","type-page","status-publish"],"acf":[],"_links":{"self":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/pages\/17022","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/users\/9575"}],"replies":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/comments?post=17022"}],"version-history":[{"count":22,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/pages\/17022\/revisions"}],"predecessor-version":[{"id":39484,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/pages\/17022\/revisions\/39484"}],"wp:attachment":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/media?parent=17022"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}