Can you clean a HEPA filter? If so, how should you wash or clean a air purifier filter?
These questions keep cropping up, as they’re just about the only remaining problem for HEPA filters.
HEPA filters are almost perfect: they are backed by tons of scientific tests; they’re pretty cheap; they use about as much energy as a lightbulb; and they even have documented health benefits. But replacing them as opposed to cleaning them isn’t ideal. It would be great if we can clean and wash and re-use HEPA filters.
Some ‘Experts’ Say You Can Clean HEPA Filters
On the question-answer site Quora, I’ve seen industry insiders say you can clean HEPA filters by banging the HEPA filter to get the dust out:
Some people even say you can clean HEPA filters by vacuuming them:
…or even by washing HEPA filters with water. Yet other experts say you can NEVER clean HEPA filters.
But one thing I haven’t seen is anyone actually test the question and present the data. To get to the bottom of whether we should clean HEPA filters, and the best way to clean them, Smart Air engineer CK tested washing, cleaning, and vacuuming HEPA filters in the Smart Air lab.
When you search for “how to clean HEPA filter,” you will see two methods to clean HEPA filters: vacuuming and washing. Smart Air put both of these to the test.
1. Cleaning HEPA filters by Vacuuming
The first test we tried was vacuuming HEPA filters. We took a dirty HEPA filter, ran tests on its performance before cleaning, vacuumed it, and then ran more performance tests after cleaning it. In all, 8 dirty HEPAs which had been used for 3-4 months in Beijing air were tested.
Testing Effectiveness of Vacuumed HEPA Filters
For each cleaning method, CK ran 3 types of tests to measure the performance increase or decrease in the HEPA filter before and after cleaning. CK tested:
- Particle Capture: To see how cleaning the HEPA filter impacted capture performance, the percentage of 0.3 micron particles by the HEPA was measured before and after cleaning. 0.3 micron particles are a great benchmark because they are the hardest particle size for HEPAs to capture.
- Air Flow: The amount of air traveling through the HEPA filter before and after cleaning can tell us if the HEPA filter is less clogged, or if the fibers in the HEPA filter have been damaged due to washing.
- CADR: CADR is the ‘gold standard’ for measuring an air purifier’s performance. It measured the total combined impact (particle capture + air flow) of washing on the HEPA filter
Here’s how the 8 HEPA filters that were vacuumed performed before and after cleaning:
Should You Vacuum HEPA Filters: Results
On average, vacuuming increased 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, cleaning a HEPA by vacuuming might help a little, but there’s also a decent chance it’ll do nothing at all, or it could even damage your filter.
What’s The Vacuum Doing to the HEPA Filter?
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.
Vacuuming bottom line: 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.
2. Cleaning HEPA filters by Washing With Water
Vacuuming did very little to improve the HEPA filters’ effectiveness. So, how about washing HEPA filters instead? This time, CK tested 3 HEPA filters by washing them under a shower head (with water only) and then leaving them to dry for a day.
Should You Wash HEPA Filters With Water: Results
I stopped testing after 3 trials because the results were so conclusive: washing HEPA filters with water decreased effectiveness by an average of 32%.
Why Is It Bad to Wash HEPA Filters?
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.
First, washing actually increased the amount of air passing through the HEPA filter.
Great, right!? But then the particle capture of the HEPA filter actually went down a lot after washing.
Washing the HEPA filters probably broke some of the fibers or made the gaps between the fibers larger. That would explain why more air passed through after washing, but also more particles!
Washing bottom line: Washing HEPA filters with water significantly decreases performance.
Read More: How to Know When to Change My HEPA Filter?
Bottom Line: How to Clean and Wash a HEPA Filter?
- Vacuuming HEPAs may improve performance, but the effect is small.
- Washing HEPAs strongly decreases performance. We do not recommend washing HEPAs.
Therefore, HEPA filters should still be replaced when it starts to get clogged and its effectiveness dropped. When is this? Learn why the standard numbers might not always be accurate.
Washing & Cleaning HEPA Filters: Open Data
You can learn more about the testing methods and view the original data in the supplemental data article.
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Mmmhm, personally I’d like a less efficient HEPA filter that allows it being cleaned by washing or something as it would help with creating less garbage that can’t even be recycled and to me that’s usually a big problem.
Hi Carlos! Song here from Smart Air. Lower-grade HEPA filters could be similarly damaged if being phusically/chemically cleaned. We also hate to create much waste and really hope they can be reused and recycled. Here are some tips that may mitigate the pollution.
wouldn’t vacuuming the filter release all the particulates into the air via the exhaust on the vacuum ? e.g. into your house if done inside
Great question Rob! This depends ont he type of vacuum cleaner you use – if you have a HEPA vacuum then it will be able to capture the particles. If not, then you could well be re-releasing particles back into the air. This is another reason why vacuuming HEPAs probably isn’t the best solution
Sometimes vacuuming is the only option. I live in a 3rd world country. I bought two air cleaners and one vacuum all with hepa filters from three different manufacturers. Unfortunately none of them have replacement filters available. Which seems like a stupid way to lose businesses. I contacted all three manufacturers. They either ignore my messages are impossible to get a live person or refer to one of their authorized service “centers” for parts. But when i contact multiple centers they all say they do not carry replacement hepa filters and that they have parts only for repairs of broken machine. It seems very stupid but the way they do a lot of things here doez not make sense to me. So i just vacuum or try to tap clean by hand when filter is full and clogged. But at least i live close to the sea and my life here is relatively stress free, so overall i can not complain too munch
That really sucks, Eurich. I’ve seen many purifier manufacturers that sell the purifier, but not replacement filters. They make a quick buck selling the purifier then don’t want to deal with the rest. It’s worth trying to find a purifier company that guarantees and commits to providing spare filters.
In your case, however, vacuuming is a reasonable option to extend the lifespan of your filters. Another option could be to try and find filters of comparable sizes from other brands that will fit into your purifier. This can often be a cheap and effective way of purchasing replacement filters!
I think the tests should be done with a NEW HEPA filter, not with dirty one. Do test wind speed and particles captured on a new and clean HEPA filter; then wash/shower that new filter, let dry and do the tests again. If results differs, the washing damaged the new HEPA filter. But if results are the same or so, my intuition tells me that, when you wash a dirty filter, wind speed increases due to cleanness of fibers and particles captured decreases due to fiber not clogged with dirty.
That makes no sense. People don’t need to vacuum or wash new filters, just dirty ones. This is for real life and to see if people should do it or not. People don’t wash or vacuum new filters before they use them.
I’ve discovered a great device for sanitization of KN95 variety (foldable meltblown) face masks – a Nesco food dehydrator, which circulates hot air up to a nominal 71 deg C (max temp on the dial – in practice actually higher), regulated within about +/- 1 deg C, and consistent throughout the dehydrator to within about +/- 1 deg C. The trick is that the temperature dial is quite inaccurate. A good meat thermometer, ice-water-calibrated, with a remote probe, can be used to fine-tune the temperature to 70 +/- 1 deg C in the middle of the dehydrator.
I use a regimen of 70 deg C dry heat for 60 min to deactivate 99.99% of the coronavirus. This treatment is less harsh than 75 deg heat for 60 minutes, found relatively safe for masks by the NPPTL:
https://www.cdc.gov/niosh/npptl/respirators/testing/results/Decon_012_Redacted-508.pdf
And 70 deg dry heat for 60 min (actually 61 min) has been shown to deactivate 99.99% of the virions:
https://www.medrxiv.org/content/10.1101/2020.04.11.20062018v2.full.pdf
Add a 60 min countdown timer to this setup, and it’s quite convenient. The dehydrator will hold about 16 – 20 KN95 masks, laid out across 4 trays.
On the masks with hepa filter I use a UV sterilizer and after a while just throw out the mask filter and stick in another one. I use pieces of the filtrate in a mask with a filter pocket. The UV sterilizer is on Amazon
How can you tell if the UV sterilizer actually works? People have bought plenty of things off of Amazon that don’t work like promised.
I’ve been taking apart Filtrete Elite Allergen filters to use in face masks I make given the unavailability of adequate masks for us common folk. I’d been blasting the masks with my steam cleaner or steam iron and now I’ll stop with this information about a stream of water widening the airways in the filter. Another way to sterilize the filter after use would be to put it in an oven on its lowest heat, 170, or on a dryer rack at high heat setting. Or leave the mask in the dashboard of your car while it sits in the hot sun. Or put it on a dryer rack at high heat for 20 minutes. I wish you could test these filters after they’ve gone through these procedures to see if they’re ruining the masks’ filtering abilities. Pleated electrostatic furnace filters can yield a whole lot of material, enough to make many masks. If they’re an effective, safe medium and we learn how to maintain them, they could save lives.
The CDC says you can just leave the mask unused for five days or more. Letting it dry out will probably help kill any virus on it a bit faster, they don’t like it dry. They suggest putting it in a paper bag labelled with your name. Some hospitals in the US are doing this, 5 masks per healthcare worker…
https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html
See “The Best Way to Disinfect Masks Without Destroying Them”: https://smartairfilters.com/en/blog/disinfect-clean-n95-mask-virus-coronavirus/
Hopefully there’s no fiberglass in them.
Hmm. What causes a filter to lose effectivness? My intuition says that the spaces between the fibers get plugged with particles.
What about this: Wash a HEPA filter. Now has decreased drag and decreased capture. But is is now usable as a pre-filter for the new filter, and would it extend the new filter’s life.
Other places where you use this strategy: My pond water filtration has a coarse screen on the inlet to keep from sucking in weeds. Then a sand filter, then a 400 micron screen filter then a 70 micron disk filter. Each can be back flushed. Each filter reduces the load on the following filter.
When I ran a darkroom, the wash cycles were staged. Prints were washed 3 times each in a tray that caught the overflow form the following tray. So the prints went tray 1,2,3 but the water flowed 3,2,1. So the cleanest water was used to get the last bit of fixer out of the paper, while the worst water was used to get the first and largest lot of chemical out.
This is pretty much the exact same mechanism with HEPA filters. After use, they get clogged, reducing the airflow. However, if you clean your HEPA filter you may well damage the fibers so much that it ends up not being able to capture many particles. Our data on washing HEPA filters with water above shows this.
What about using pre filters over them for catching larger particles then washing pre filters
This is the exact purpose of a pre-filter! They are smaller filters designed to catch the larger particles, which can then be washed or replaced more easily. It helps prolong the lifespan of the HEPA filter, but capturing most of the large particles and stopping the HEPA filter from getting clogged.
Hello! Is it possible to use a blower to clean HEPA filters, at least superficially? To be specific, I’ve been using the Sqair for only a little over a month, but there’s already a significant amount of dust (and dust bunnies?) in the filter (I don’t use a pre-filter). I was wondering if such visible amounts of dust affect cleaning performance. My hunch is that blowing the filter would also damage it–would that be correct?
Hi Amogh, if you read the article, we tried to vacuum the HEPA filter. I guess blowing it would be about the same effect. Some dust can get out, but the CADR will not increase dramatically. Here is a test we did or the HEPA lifespan, it tells how the HEPA efficiency changes as time passes: https://smartairfilters.com/en/blog/sqair-hepa-lifespan-test/
I don’t suggest to clean the HEPA filter, if you live in a place with heavy dust, cover the grill on top with a clean and dry cloth when you don’t use it. And when you use it, since the air is blowing from the bottom to the top, not much heavy dust will settle in the fan or HEPA since the airflow can help to lift them off.
I work at a humane society, and we have Hepa filters mounted in ceiling in our surgery suites. I have read some articles about cleaning them, washing them with water will damage them i believe. Vacuuming them doesnt seem that would clean them thourgh enough. The filters i need to replace are very costly, any sugestions on how to clean? Trying to avoid replacing due to cost, but i may have to. If i have to replace with new ones, how often would you sugest?
Hey David! I’ve been researching washable and/or re-useable HEPA filters for 4 years and unfortunately have yet to see any viable solutions to this. Right now the only really viable option is to replace them. You could consider putting washable pre-filters before your HEPA filters (they are coarse, thick filters which can capture dust and larger particles, hence extending the lifespan of your HEPA filter) but you will need to check that your system can handle the extra workload caused by pushing air through an extra filter.
Having said all this, HEPA filter technology was invented over 70 years ago, and it’s free & open tech (no patents as such). If you’re being charged a lot for your replacement filters, you could consider looking elsewhere for cheaper filters – they’ll likely work just as well, just like we found when creating our DIY air purifiers.
I vacuumed my Kenmore 85150 PlasmaWave AirCleaner’s hepafilter and carbon filter. They looked pretty good after, without the obvious loose fibers that you show in the image above. Can’t say that some particles haven’t been disturbed. More importantly, though, I reset the “change filter” light – it went off right away and hasn’t returned for more than an hour. It seems that the machine would know if the filters are doing the job. What do you think?
Hey Rob, interesting you’ve tried this on your Kenmore! That’s a good question on the ‘change filter’ light. I can’t speak for the Kenmore you have, but most ‘change filter’ functions work on a simple timer basis. The timer counts down from a fixed number of hours, then the light comes after exceeding this time. What this means is that when you reset the light, it normally just resets the timer. I’d say that unless you have an air quality monitor, it will be very difficult to know if it’s improved the filtering efficiency of the Kenmore or not.
It would be interesting to wash the HEPAs in non-water liquid. Ethanol or Isopropyl alcohol instead. Or even use some chemicals (Tetrachloroethylene…) they use in dry-clenaning where they wash suits and other stuff you just can’t put in washing machine.
I am really a novice in “clean air technology” but I once washed my Roomba’s old hepa-style filter in water and it became soft etc (well it was wet – no surprise. And this probably made some changes you described in this article ). But when I tried to was it in Isopropyl alcohol the filter remained rigid like it was dry. And it washed the dirt quite fine out of the filter.
This has been tested for N95 masks (similar materials). It does not work. The filter looks better, but it is damaged, perhaps because the electrostatic charge on the filter is destroyed; its performance drops dramatically. Sorry.
https://gh.bmj.com/content/5/5/e002553
We’ve now tested washing N95 masks with water and alcohol. J Larson – you’re right! Washing N95 masks is not recommended and can damage the masks.
Thanks, Paddy Robertson, for the link and the confirmation!
Could you test whether the static charge can be restored by rubbing the filter with latex gloves or a latex balloon, and whether this restores the filtration efficiency? This would also test whether washing with soap and water causes mechanical damage, destroys the charge, or both.
Evidence that this might work with polypropylene:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7294826/
(OFF-TOPIC DIGRESSION)
There’s also the suggestion that cloth masks, if made using carefully-selected separate layers for mechanical and electrostatic filtration, as disposable masks are, may work about as well as the disposable masks:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7185834/
I’d love to see some data on electrostatic charge creation in homemade masks, or restoration in alcohol- or water-washed commercial masks. I realize these suggestions would fit better on the page you linked to, but for some reason I don’t seem to be able to post to the comments there.
Managed to post to that page by loading it through the “Here’s what else you should know about:” link. Dear Moderator, please feel free to remove everything below “(OFF-TOPIC DIGRESSION)” , as I can’t edit the comment.
Really appreciate this post – thanks!
Since these filters trap particles, I wonder why you did not include testing for vibration during reversed fan direction?
You mention “banging” – did you test vibration at all, to first dislodge particles?
If you’re not comfortable using a massage vibrator, perhaps tapping with drumsticks while aiming downward?
If compressed air or vacuuming is too violent, what of simply reversing direction and using the same fan?
I’ve a vacuum cleaner from Electrolux that uses a HEPA filter, when I want to clean it I put it inside a plastic bag and then beat it to take off some of the dust then I clean the remaining dust with compressed air, wich makes a big mess, but works. I’ve tried just washing the filter but it never dries.
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.
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!
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!
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.
the operating manuals for old (10 years) dirt devil vacs with hepa filters tell you to rinse them periodically to clean, and replace a couple times a year? or somesuch. Not sure how much good it did. Also not sure that dirt devil operating manuals still say this.
Similarly, operating manuals for many window ac units (even ones that are five years old)say to rinse the filters clean when notification comes on. These filters look just like the air purifier filter pictured above.