{"id":5463,"date":"2024-10-23T17:40:33","date_gmt":"2024-10-23T09:40:33","guid":{"rendered":"https:\/\/smartairfilters.com\/?p=5463"},"modified":"2026-03-09T14:49:39","modified_gmt":"2026-03-09T06:49:39","slug":"data-explains-never-use-purifiers-auto-mode","status":"publish","type":"post","link":"https:\/\/smartairfilters.com\/en\/blog\/data-explains-never-use-purifiers-auto-mode\/","title":{"rendered":"Why Auto Mode on Xiaomi, Philips, and Levoit Air Purifiers is a Mistake"},"content":{"rendered":"
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Many air purifier companies add fancy features to help market their products.  One of these features is an air purifier auto mode, also called “smart mode”. The problem? Test data shows an air purifier’s auto mode routinely fails, leaving users with dangerous air.<\/section>\n
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The idea behind smart purifiers\u2019 auto mode is simple. The purifier has a small air quality monitor inside. When the air is bad, the purifier turns on. After the air gets better, the purifier goes to sleep.  The benefits are obvious. The purifier will use less energy and make less noise since it can spend more time at a low speed.<\/section>\n<\/section>\n<\/section>\n<\/section>\n<\/section>\n
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\"How<\/figure><\/div>\n\n\n

Real-World Tests of Air Purifier Auto Modes<\/h2>\n\n\n\n

Smart Air co-founder Anna tested two of the most popular air purifier auto modes\u2014the Xiaomi 2 and the Philips AC4072.<\/p>\n\n\n

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\"Xiaomi<\/figure><\/div>\n\n\n

These tests are simple and realistic. Over 13 days in an ordinary 15<\/span>m2<\/sup><\/span><\/sup> <\/span>Beijing apartment, Anna turned the Xiaomi or the Philips on auto mode before bed.<\/p>\n\n\n

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\"Apartment<\/figure><\/div>\n\n\n

She used a\u00a0Dylos Pro laser particle counter<\/a>\u00a0to track 0.5-micron and 2.5-micron particles every hour until she woke up in the morning. The Dylos has shown high accuracy (r = .89) in several\u00a0comparison tests with official PM2.5 numbers<\/a>\u00a0(1<\/a>,\u00a02<\/a>). I calculated percentage reductions from before turning on the purifier versus the average over the last four hours before waking up.<\/p>\n\n\n

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\"Xiaomi<\/figure><\/div>\n\n\n

Results: Air Purifier on Auto Mode Left Air Dirty<\/span><\/strong><\/h2>\n\n\n\n

The pictures below show the Xiaomi at the start and end of a test. Despite running in a closed room all night, the Xiaomi auto mode left indoor air in the unsafe range.<\/p>\n\n\n

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\"Indoor<\/figure><\/div>\n\n
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\"Indoor<\/figure><\/div>\n\n\n

Xiaomi averaged a 62% reduction, and Philips averaged a 59% reduction.<\/p>\n\n\n

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\"Auto<\/figure><\/div>\n\n\n

For comparison, this is more than 20% worse than what I found by just strapping a filter to a small fan<\/a> with a Velcro strap.<\/p>\n\n\n

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\"Average<\/figure><\/div>\n\n\n

But wait, maybe the Philips and Xiaomi are just bad purifiers. Maybe they use low-grade filters, or maybe their fans aren\u2019t strong enough.<\/p>\n\n\n\n

Is There a Problem with the Air Purifiers?<\/h3>\n\n\n\n

Our other tests say no. In tests of the high setting, the Philips scored near the top of my earlier comparison tests<\/a>.<\/p>\n\n\n

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\"Air<\/figure><\/div>\n\n\n

And in\u00a0<\/span>tests of Xiaomi\u2019s high setting<\/a>, it also performed relatively well but cannot be kept on high.\u00a0The machine switches to auto mode whether users want it or not at the third hour.\u00a0\u00a0Really? You really can’t set the Xiaomi to stay on high?<\/a>\u00a0<\/span><\/p>\n\n\n

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\"Xiaomi<\/figure><\/div>\n\n\n

But is it Actually Unsafe?<\/h3>\n\n\n\n

OK, OK, skeptical readers might say, \u201cWell a 60% reduction isn\u2019t bad. Isn\u2019t that good enough?\u201d<\/p>\n\n\n\n

It\u2019s certainly better than nothing, but based on my reading of the\u00a0research on the health effects of air pollution<\/a>, this is meaningfully bad air. On average, indoor air was double the WHO 24-hour PM2.5\u00a0limit<\/a>\u00a0(and that\u2019s the loser of their limits!).<\/p>\n\n\n

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\"Auto<\/figure><\/div>\n\n\n

Why Are Air Purifier Auto Modes So Bad?<\/h2>\n\n\n\n

The tests on the high setting above showed that it isn\u2019t a problem with the fan or the filter. These machines work well on high. So what explains it?<\/p>\n\n\n\n

Cause 1: The Built-In Air Quality Monitor is Wildly Inaccurate<\/h3>\n\n\n\n

The auto mode is governed by the built-in air quality monitor. The problem is, that I systematically tested three different Xiaomi\u2019s against three independent particle counters and found the\u00a0Xiaomi monitor was wildly inaccurate<\/a>. At its worst, it was underestimating actual PM2.5 by 218 micrograms!<\/p>\n\n\n

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\"Xiaomi<\/figure><\/div>\n\n\n

So sometimes these machines might think the air is safe when \u201ctoxic\u201d would be a more accurate description.<\/p>\n\n\n\n

Cause 2: The Xiaomi Has a Loose Definition of \u201cSafe Air\u201d<\/h3>\n\n\n\n

It could also be that they just have a loose definition of \u201csafe air.\u201d For example, China\u2019s PM2.5 limit is 35 micrograms, whereas the World Health Organization\u2019s annual limit<\/a> is 5 micrograms.<\/p>\n\n\n\n

Levoit Air Purifier Auto Mode<\/h2>\n\n\n\n

Not only do Xiaomi and Philips air purifiers have built-in auto mode, but Levoit air purifiers, one of the best-sellers on Amazon, also offer this feature. The same issue here, they consider 0-35\u00b5g\/m3 as VERY GOOD<\/strong> which follows the Chinese standard (‘good’ is 0-35\u00b5g\/m3). However, the air quality isn’t good at all when it reaches 35\u00b5g\/m3, 7 times higher than the WHO annual limit.<\/p>\n\n\n

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\"Levoit
\u00a9Levoit<\/figcaption><\/figure><\/div>\n\n
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\"levoit
\u00a9Levoit<\/figcaption><\/figure><\/div>\n\n
Bottom Line<\/div>
Bottom Line: <\/span>What Users Should Know About Purifier\u2019s Auto Mode<span><\/div>
<\/span><\/p>\n

Auto modes routinely leave indoor air far above safe limits. I do not recommend using auto modes (or the Mi2, which\u00a0forces people to use auto mode after three hours<\/a>). <\/div>

Smart Air<\/div><\/div>\n\n\n\n

Open Data<\/h3>\n\n\n\n

As always, I\u2019m publishing the original data and more details on the test method for fellow nerds. They are available <\/span>here<\/span><\/a>.<\/p>\n\n\n\n

<\/p>","protected":false},"excerpt":{"rendered":"

Many air purifier companies add fancy features to help market their products.  One of these features is an air purifier auto mode, also called “smart mode”. The problem? Test data shows an air purifier’s auto mode routinely fails, leaving users with dangerous air. The idea behind smart purifiers\u2019 auto mode … <\/p>\n

Read more<\/a><\/p>\n","protected":false},"author":1035,"featured_media":41238,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","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":"5189,3961,21680,3981,28033,22029","_relevanssi_noindex_reason":"","footnotes":""},"categories":[190,262],"tags":[283,285],"class_list":["post-5463","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-air-purifiers","category-reviews","tag-air-purifier","tag-review","resize-featured-image"],"acf":[],"_links":{"self":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts\/5463","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/users\/1035"}],"replies":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/comments?post=5463"}],"version-history":[{"count":34,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts\/5463\/revisions"}],"predecessor-version":[{"id":34373,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts\/5463\/revisions\/34373"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/media\/41238"}],"wp:attachment":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/media?parent=5463"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/categories?post=5463"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/tags?post=5463"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}