Working on DIY air purifiers for over 6 years, I’ve heard from a lot of people who have strong intuitions about cleaning car air filters. People tell me they wash their vehicle’s air filter, vacuum it, or bang it really hard. Opinions are plenty, but what about real, hard data?
Can you clean air filters – the data?
Smart Air’s hard-working engineering intern CK vacuumed and washed several Beijing-level-dirty HEPA filters (this type of HEPA filter, to be exact) in Smart Air’s Beijing laboratory.
The results? Washing lowered performance by 30%. Vacuuming improved performance by 10% on average, but for some filters, it actually lowered performance. Get the full story on washing and vacuuming tests here.
Can you clean a filter with compressed air?
But what about compressed air? The other answer here says this is the “definitive way to clean filters.” So some people believe it. Does the data believe it?
I haven’t tested it, but these car guys in Guangzhou tested car air filters with compressed air (in Chinese).
They tested a new filter and a really gross old filter. Then they cleaned the old filter with compressed air.
They put the filter in the car’s air system, and ran the air system on the medium setting for 5 minutes. They used a laser particle counter to track the amount of particulate in the air.
I put their data into a graph below. Over 5 minutes, the filter reduced particulate from 150 micrograms to around 30 micrograms.
However, cleaning the filter with compressed air actually made it worse! Based on their data, you’d be better off using the dirty filter (and best off with a new filter, of course).
Bottom line: Compressed air is not a good way to clean a filter – be it a car filter or any other type of air filter.
Are there other ways to clean a car air filter?
My tests showed vacuuming improved performance by 10% on average, but the benefit is small and probably not worth the hassle. The only cleaning I’d recommend is if there’s a lot of thick, easily removable debris on the filter, like leaves or cat hair. Otherwise, get a new filter!
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.