{"id":594,"date":"2019-03-15T09:46:06","date_gmt":"2019-03-15T09:46:06","guid":{"rendered":"https:\/\/smartairfilters.com\/mn\/?p=594"},"modified":"2019-06-30T13:29:49","modified_gmt":"2019-06-30T13:29:49","slug":"do-we-need-car-air-purifiers","status":"publish","type":"post","link":"https:\/\/smartairfilters.com\/mn\/en\/blog\/do-we-need-car-air-purifiers\/","title":{"rendered":"Do We Need Car Air Purifiers?"},"content":{"rendered":"

Car air purifiers sound like a great idea. Soon after I started\u00a0<\/span>making DIYs<\/a>, people emailed me asking if we could make a DIY for their car. My initial reaction was, \u201cGreat idea!\u201d On the highways, we\u2019re surrounded by all of that awful pollution. Best to get a car air purifier.<\/p>\n

But as a methodical nerd, I wanted to do some tests first. The results of those tests led me to a conclusion I didn\u2019t expect: you don\u2019t need a car purifier. Here\u2019s how I got to that conclusion.<\/p>\n

Uber Test<\/strong><\/p>\n

I took to the streets of Shanghai with my\u00a0<\/span>Dylos DC1700<\/a>\u00a0<\/span>laser particle counter. (Are particle counters accurate?<\/a>) Here\u2019s what the air outside was like:<\/p>\n

<\/p>\n

The number on the left is the number of particles 0.5 microns and above. For that channel, \u201csafe\u201d is somewhere around 2,500. So the air that day wasn\u2019t pretty. The number on the right is larger particles\u20142.5 microns and above.<\/p>\n

Results<\/strong><\/p>\n

Next, I got into an Uber and kept taking readings. Here\u2019s what the air was like when I just got into the car:<\/p>\n

\"car<\/p>\n

Way better! The 0.5 micron particles were only about 25% of outdoor air.<\/p>\n

And a few minutes later:<\/p>\n

\"car<\/p>\n

 <\/p>\n

Look, ma, no purifier! We were down to 11% of outdoor air.<\/p>\n

So why\u2019s the air so much cleaner?<\/strong><\/p>\n

It turns out car air systems have filters in them already, and apparently they do a pretty good job of filtering out particulate pollution.\u00a0<\/span>Here\u2019s an example of a car filter on Amazon<\/a>\u00a0<\/span>for only around $10.<\/p>\n

<\/p>\n

 <\/p>\n

Tests in a Regular Car<\/strong><\/p>\n

This simple test suggested to me that the car\u2019s built-in air filtration system reduced particulate levels significantly\u2014even the dreaded particles smaller than 2.5 microns. But was it something special about that car?<\/p>\n

To be sure, I teamed up with Ohad, a Smart Air aficionado to do tests in his Mazda in Israel. He drives a regular 2010 Mazda 3\u2013no special filters.<\/p>\n

\"car<\/p>\n

Method<\/strong><\/p>\n

Ohad took his Dylos particle counter with him when he drove his car. When he got in the car, he turned on the AC, used \u201crecirculate air\u201d mode, and kept the windows closed. That\u2019s it. Ohad took measurements every minute for five minutes. That\u2019s not very long, so this is a fairly conservative test of the car cabin.<\/p>\n

But wait, does Israel really have bad air pollution? It\u2019s no Beijing, but several parts of Israel have recently\u00a0<\/span>experienced dangerous levels of smog<\/a>. In Ohad\u2019s tests, baseline 0.5 micron counts ranged from 2,464 (near the WHO limit) to over 10,000 (four times the limit). So the air has plenty of particulate to do tests.<\/p>\n

Results<\/strong><\/p>\n

I averaged across all 8 tests, and here\u2019s what I found:<\/p>\n

\"Car<\/p>\n

The Mazda\u2019s built-in air filtration system drastically reduced the number of particles. When averaged over the course of 5 minutes with the fan on its maximum setting, the results showed a staggering 97% reduction of 0.5 micron particles and 99% drop in 2.5 micron particles!<\/p>\n

But wait, savvy readers might ask: how do we know it\u2019s the car\u2019s air system and not just that there\u2019s a person breathing in all those particles? Or maybe it\u2019s because\u00a0<\/span>particles settle over time<\/a>?<\/p>\n

Ohad also ran an identical test with the car air system turned off. That way we can know if the reduction is truly because of the air system.<\/p>\n

\"Car<\/p>\n

With the air system off (the red line), particle levels drop a bit, probably because of settling.But with the air system on (blue line), particulate levels dropped much faster.<\/p>\n

Across 5 tests with the AC off, particulate went down (right), but not nearly as much compared to the 8 tests with the AC on high (left):<\/p>\n

\"Car<\/p>\n

Conclusion<\/strong><\/p>\n

After seeing the data, I\u2019m convinced we don\u2019t need special car purifiers to protect against particulate pollution. The air systems already in cars dramatically reduce particulate pollution.Here\u2019s how to do it:<\/p>\n

1. Keep the car windows closed.<\/p>\n

2. Use the \u201crecirculate air\u201d mode for the highest particulate drop.<\/p>\n

3. Turn the fan on high (at least at the beginning of the trip).<\/p>\n

4. Check and replace your filters every few months.<\/p>\n

5. Think twice about whether you really need a car purifier.<\/p>\n

Exception: Gas pollution<\/strong><\/p>\n

There is one exception to these tests: Car filters capture particles, but they won\u2019t capture gases, like NO2. Thus, it may still be worthwhile to consider using a carbon filter. (Does carbon really work?<\/a>)<\/p>\n

Are you saying no one should ever use a car purifier?<\/strong><\/p>\n

If I owned a car in China, I wouldn\u2019t bother buying a car purifier, but I won\u2019t say\u00a0<\/span>no one\u00a0<\/strong>should buy one. For example, people who are extra sensitive to pollution or parents with small children might consider using a purifier to get extra protection.<\/p>\n

As always, I\u2019m making\u00a0<\/span>the raw data and more testing details publicly available<\/a>\u00a0<\/span>for fellow nerds. Check that test out for a full comparison of AC high, AC low, and AC off tests.<\/p>\n

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

Car air purifiers sound like a great idea. Soon after I started\u00a0making DIYs, people emailed me asking if we could make a DIY for their car. My initial reaction was, \u201cGreat idea!\u201d On the highways, we\u2019re surrounded by all of that awful pollution. Best to get a car air purifier. … Read more<\/a><\/p>\n","protected":false},"author":4580,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-594","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/posts\/594","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/users\/4580"}],"replies":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/comments?post=594"}],"version-history":[{"count":4,"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/posts\/594\/revisions"}],"predecessor-version":[{"id":710,"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/posts\/594\/revisions\/710"}],"wp:attachment":[{"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/media?parent=594"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/categories?post=594"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/smartairfilters.com\/mn\/en\/wp-json\/wp\/v2\/tags?post=594"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}