Can I Clean or Wash HEPA filters?

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HEPA filters are a nearly perfect solution for air pollution. They are backed by tons of scientific tests; they’re pretty cheap; they use about as much energy as a lightbulb; they even have documented health benefits.

Just about the only remaining problem is that you have to throw out the HEPA filters every few months. So wouldn’t it be great if we could clean them and re-use them? Here we’ll try and answer how to clean HEPA filters.

 

People have lots of opinions! On the question-answer site Quora, I’ve seen people say you can clean HEPA filters by banging the HEPA to get the dust out:

 

clean a HEPA filter by banging out the dust

 

…or to clean a HEPA filter vacuuming it

 

clean a HEPA filter by vacuuming

 

…or even wash it. Then I’ve seen other people say you can NEVER wash a HEPA.

 

you can never clean a HEPA filter

 

But one thing I haven’t seen is anyone actually test the question. Well now I’ve got data. That’s because CK from Smart Air decided to test out the best way to clean a HEPA filter. Here’s CK’s story.

 

 

Vacuuming the HEPA

First I tried vacuuming a HEPA. I took a dirty HEPA filter, ran tests on its performance, vacuumed it, and then ran more performance tests. In all, I tested 8 dirty HEPAs given to us by avid Smart Air users! They all used in China for between 2-4 months.

 

Testing Effectiveness

Particle Capture: I measured the percent of 0.3 micron particles captured at the outlet of the HEPA before and after washing. 0.3 micron particles are a great benchmark because they are the hardest particle size for HEPAs to capture.

Air Flow: I measured air speed coming out of the HEPA before and after washing.

CADR: I used particle capture and air flow to estimate CADR.

 

 

Vacuum Results

On average, vacuuming increased relative CADR by about 10%. But there was also a lot of variance, ranging from a 14% increase to a 3% decrease. Based on that data, I’d say cleaning a HEPA by vacuuming it might help a little, but there’s also a decent chance it’ll do nothing at all.

 

What’s The Vacuum Doing?

HEPAs are made of thin fibers. The vacuum is probably pulling out some of the larger dust particles from the HEPA filter, but at the same time some of these fibers as well. You can see what looks like fibers that have been pulled loose in this picture.

 

HEPA

 

In short: There may be a slight benefit of vacuuming HEPAs, but the benefit is small, and it can also damage the HEPA. Therefore, we do not recommend vacuuming.


Washing the HEPA

So, what if we wash them instead? I used the same 3 filters that were vacuumed before and washed them under a shower head. Then I gave them a day to dry.

 

 

Washing Results

I stopped testing after 3 trials because the results were so conclusive: cleaning the HEPA through decreased effectiveness by an average of 32%.

 

 

Why Was Washing So Bad for the HEPAs?

To get to the bottom of why washing was so bad for the HEPAs, I looked at wind speed and particle capture before and after washing the HEPA.

First, washing actually increased the windspeed.

Great, right!? But then particle capture actually went down a lot after washing.

 

effectiveness of HEPA fitler after washing

Washing the HEPAs probably broke some of the fibers or pushed the gaps between the fibers larger. That would explain why more air passed through after washing, but also more particles!

In short: Washing HEPAs with water breaks down the HEPA material and so is not recommended.


Bottom Line

Vacuuming HEPAs may improve performance, but the effect is small. Washing HEPAs strongly decreases performance. We do not recommend washing HEPAs.

Based on this data, it seems it really is not possible to clean your HEPA filter. We still recommend replacing your HEPA when its effectiveness drops. When is this? We tested this with the Smart Air DIY air purifier found replacing after 140 days is best. For the larger HEPAs, like those in the Blast and Blast Mini purifiers the huge surface area means they can last over 1 year.

Own another purifier? Learn why the standard numbers might not always be accurate.

Open Data

You can learn more about the testing methods, and view the original data in the Supplemental Data article. Click here to learn more.

Choon Khin is a Smart Air engineer from Singapore, studying chemical engineering at the National University of Singapore

5 thoughts on “Can I Clean or Wash HEPA filters?

  1. Hi there,

    There are some questions that I hope could be clarify a bit more:
    1. How do you vacuum the HEPA filter, and which side of the filter do you vacuum?
    2. I do not by any means say that you made up this data. I totally believe that you guys would do whatever it takes to lower down the cost, not for yourselves, but for the customers. However, I think you are testing the wrong HEPA filters, which are not created to be cleaned again. Many vendors have official guidance of how to maintain their Air Purifiers or Vacuum Cleaners:
    – Honeywell: 17000-S (https://www.honeywellpluggedin.com/air-purifiers/honeywell-true-hepa-allergen-remover) and 50250-S (https://www.honeywellstore.com/store/products/honeywell-50250-true-hepa-germ-fighting-allergen-reducer-air-purifier.htm) are used to be claimed “with Permanent HEPA”. Though later on they were changed to be “Long life HEPA”, their filters are still very effective for years after periodically vacuum cleaning (NOT washing with water). 50250 was even listed as Top 5 Best Air Purifiers by Consumer Reports as of May 2017 (the only one I could find for free on the Internet).
    – Sharp: one model I know that has instruction to clean HEPA filter by vacuum it, is FP-G50E-W (https://sharp.ph/product-list/fp-fg50e-w/).
    – HEPA washable vacuum cleaner: I have read some but right now could not find any. Sorry.

    As some of the team are in the US, hopefully you guys could repeat your test with any of the used HEPA filters listed above.

    Breathe safe!

    1. Hi Tu Ngyuen, Paddy here in Beijing, who performed these tests along with CK! I’ve also seen reports of ‘washable HEPAs’, and when we initially wanted to do this piece of research, our first idea was to go out and buy a ‘washable HEPA’ and test that (why, after all, would you want to wash a HEPA filter that’s not labelled as ‘washable’!?). After lots of searching, we couldn’t find any purifiers that actually said you could wash the HEPA filter. To us it seemed like these companies were claiming something that was too good to be true. Having said that, you’re right – if we really can get our hands on what a company claims is a ‘washable HEPA’ then we will definitely test it!

      1. Hi Paddy,

        Actually I am suggesting you guys testing on the ‘vacuum-able HEPA’, like the Honeywell 17000 or 50250. Unfortunately they are not sold outside US and Canada, so only guys who are living in US can conduct this test. Only one HEPA filter for Air Purifiers I’ve known about is washable, from Electrolux: http://homeappliance.manualsonline.com/manuals/mfg/electrolux/elap40.html?p=11.

        But for the Vacuum cleaners, yes, there are some, mostly known from Electrolux also. Here is one HEPA H12 washable filter EF H12W for Electrolux cycloneXL vacuum cleaner: http://homeappliance.manualsonline.com/manuals/mfg/electrolux/elap40.html?p=11

        I totally agree that HEPA filter efficiency will be decreased the longer we use it. However cleaning the right filter the right way should prolong its life cycle. Or maybe I am blindly believe in whatever the manufactures are telling us, who knows? I really wish that you guys could test it and reveal the myths.

    1. That’s a good idea Rodrigo! Bashing a HEPA can get rid of some of the larger pollution particles (like PM10) which could definitely increase the lifespan of the HEPA filter. We didn’t test this method in our series of tests but it’s definitely something to consider. How long it will increase the HEPA lifespan for, and how often you’d need to do it is difficult to say.

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