How to Clean a HEPA Filter

Before we dive into how to clean a HEPA filter, there’s one question we MUST answer. Can HEPA filters be washed or cleaned in the first place? In this post, I’ll answer this all-important question and more. I’ll help you understand how to take care of your HEPA or HEPA-type air purifier filters so you can get the most bang for your buck.

As you know, well-maintained items tend to serve the user more efficiently and longer. And that ends up saving the consumer  money. But wh0 says you must use an air purifier that uses HEPA filters? Why not buy the best air purifier with washable filter your budget can accommodate and stop worrying about how to clean a HEPA filter and other related boring stuff?

What Are HEPA Filters?

According to the EPA, a HEPA filter is a kind of mechanical air filter. The term HEPA is an acronym for High Efficiency Particulate Air. These filters have been shown to eliminate at least 99.97% of PM2.5 particles, those with a diameter of 0.3 microns. These PM2.5 particles include household dust, pollen, bacteria, mold, and more.

Why 0.3-micron particles, you may ask. It’s because these particles happen to be the most penetrating particle size. If not taken care of, they might travel to the most delicate and irreplaceable organs and damage them. You know the brain, heart, lungs, name it.

What about PM2.5 particles with a sub-0.3-micron diameter? The EPA further states that HEPA filters demonstrate even greater efficiency when it comes to trapping smaller or larger particles. There’s tons of confusion out there concerning whether HEPA filters are any good for PM2.5. And I guess this explanation from the EPA adequately and clearly answers that all-important question.

Can HEPA Filters Be Washed?

Yes, some HEPA filters can be cleaned.  But can you clean a HEPA filter with water? Yes, you can if, you choose to do that. However, it’s just not a good idea to wash them using soap and water. In most cases, washing them like that decimates their effectiveness.

The filter might look OK after you wash and dry them, but the truth is that washing them ruins them considerably. You won’t find any studies explaining whether it’s ok or not to wash HEPA filters, though.

Luckily for you, I came across one small study conducted by an expert I respect. And I’ll share the results they saw so that we can get this question out of the way once and for all.

So, you can clean HEPA filters. But you should think again before taking a brush, soap, and a bucket full of water to wash them. Or even before you rinse them out in the kitchen faucet.

Not All HEPA Filters Are Washable

While some HEPA filters can be cleaned without issues, some just can’t or shouldn’t be washed. So, how do you know if your HEPA filter is washable? Obviously, the best way to find out is to devour the user’s manual. Manufacturers typically state whether a filter is washable or not. Or whether the filter is permanent or disposable.

If the manufacturer has stated that the filter should be replaced rather than washed, it’s best to do just that. But what would happen if you decided to wash the HEPA anyway? I don’t know. Why not try it and see what happens? You can wash and put back the filter into the device, but you certainly won’t get as much performance as you’d like. In my opinion, it’s best to replace disposable replacement HEPA filters.

Safety First

Yes, I understand. You and pretty much everyone who uses air purifiers would want to save a buck here and another there. And yes, high-quality replacement filters don’t come cheap. In fact, some can be obscenely expensive. Believe it or not, I’ve seen replacement filters (HYPERHEPA) that cost north of $300!Folks who care about indoor air quality are ok with shelling out that much for replacement filters. Why?

It’s because new filters certainly work better than reused one, generally. Such people cringe at the thought of getting a respiratory illness down the road. But using an effective air purifier doesn’t guarantee 100% protection against the effects of indoor air pollution. That said, we all know that less indoor air pollution translates into reduced exposure to disease-causing agents.

Remember the small study I told you about? It’s time to present the findings.

Washing Vs Vacuuming Vs Using an Air Compressor on HEPA Filters

Wouldn’t it be nice to be able to save tons of money over the long term on HEPA replacement filters?Having to replace filters is about the only bad thing about owning a HEPA air purifier. But are HEPA air filters washable?

Some people say they are. Others they you should NEVER wash a HEPA filter. And others think you can wash them half the time and replace them the rest of the time. But who’s right and who’s wrong?

Thomas Talhelm of the University of Chicago owns a small company that makes air cleaning devices. I’m not here to sing his praises, though. But I need to tell you he recently tested 3 HEPA filter cleaning methods and found interesting findings.

Assistant Professor Talhelm asked one of his technicians to test how washing, vacuuming, or using an air compressor impacted a purifier’s performance. Once you see the results, you won’t want to wash your filter ever again!


The technician fetched 8 dirty HEPA filters from the company’s storeroom and tested them, noting down the performance of each. All of the filters had loads of dirt and filth collected from some of the dirtiest indoor on Earth — China’s indoor air.

Then, he vacuumed the filters and tested them, recording the effectiveness of each. He tested the effectiveness measuring particle capture before and after vacuuming. Next, he repeated this procedure for the other two cleaning methods, washing and using an air compressor. In addition, the researcher measured airflow and estimated each filter’s CADR (Clean Air Delivery Rate) before and after testing.

Results from Vacuuming 8 Dirty HEPA Filters

He found that vacuuming the HEPA filters increased the CADR by 5.43% on average. The largest performance improved hovered around 13 percent. And the smallest change was actually a deterioration of 2.5%. In one of the 8 filters, there’s was no change, and another filter saw a negligible change of 0.9%.

Conclusion: Vacuuming a HEPA filter often improves its performance. However, there’s a possibility it won’t improve it one bit.

What was there a decline in performance in some filters? It’s possible the vacuum cleaner pulled loose some filters, weakening the overall structure of the filter. As a result, dust and other particulates found chinks via which they could escape. And they did!

Results from Washing the Filters

We’ve seen that vacuuming HEPA filters may offer some benefits, but they’re not small benefits at best. So, is washing better than vacuuming?

The researchergave each of the 8 filter a quick rinse under a shower head. Then, he left them to dry out for the next 12 hours. What happened?

The results from washing the filters were extremely discouraging compared to those from vacuuming and even air-compressing the filters. They were so bad that the technician didn’t see the need to go past filter 3.

For HEPA filter #1, there was a 41.12% drop in performance! That was the worst performance in the experiment. Now, compare that with the worst performance when the filters were vacuumed: -41.12% vs 2.5%. That’s a huge difference, right? For filter #2, there was a decline of 32.61%. And for filter #3, the deterioration stood at 19.82%.  On average, washing the HEPA filters caused a staggering 31.18% decline in performance.

Conclusion: washing HEPA filters just isn’t a good idea as it reduces their performance substantially. Surprisingly, lots of people wash HEPA filters because the manufacturer said it’s the best way to restore them to acceptable performance. Yes, the filters may look clean, but understand they’ll let tons of allergens and other pollutants to pass through.

What about using an air compressor? Do the filters work better than in the case of washing or vacuuming them? Let’s see. Numbers never lie, they say.

Results from Air-compressing the Filters

Finally, let’s examine the results obtained when the filters were cleaned using compressed air. The results here actually don’t replace to HEPA filters used in regular air purifiers. Instead, the person that conducted the tests used car filters. One filter was new. The second filter acted as a control filter. It was used, but it’s not cleaned. The last filter was used, but it was cleaned using compressed air.

The findings were shocking, just like those obtained from washing. Subjecting car HEPA filters to compressed air pushed down their cleaning power significantly.

Conclusion: using compressed air to clean air purifier is an exercise in futility. It makes things worse, and it’s not something anyone should be doing after reading this article.

As you’ve seen, washing or air-compressing HEPA filters appreciably decreases their ability to remove pollutants from the air. If you have an air purifier with a permanent/washable HEPA filter, it’s best to vacuum clean it. Vacuum cleaning may also cause a bit of damage though. However, it’s much better than the other two air filter cleaning methods.

Here’s How to Clean a HEPA Filter

Unless you bought a dirt-cheap air purifier with washable filter(s), your device likely features a “clean your filter” indicator. And if your model lacks that feature, worry not. Note down the date you vacuumed the filter and the next date you should clean the filter. That way, you shouldn’t forget. You can also request your smartphone or computer to remind you when it’s time to do the job.

Steps for Cleaning HEPA Filters

We agreed you won’t wash or air-compress your filter anymore. That’s why I offer vacuuming as the only sensible solution for keeping your filters functioning optimally.

Step 1

Turn off the air purifier.

Step 2

Unplug your air purifier.

3. Step 3

Carry the device outside to some predetermined stop. You really don’t want to do the job inside the house. Why? If you vacuum the filter inside, all those debris and filth will end up where they originated — in your indoor spaces. Obviously, that’s not something you want.

Step 4

Remove the filter from the air purifier. With some purifiers, removing the filter is pretty easy. Just detach the panel at the back from the machine and pull it out.  In some devices though, the filter might be located somewhere else. With some air purifiers, you’ll have to split them apart to access the filter.

But regardless what kind of device you have, taking the filter out shouldn’t be a herculean task. And if you experience any challenges, consult the user’s manual for how to remove the filter for your model. Misplaced the manual? No worries, visit the manufacturer’s website and download the user manual there.

Step 5

Hold the filter and tap it gently, letting loose debris and other dirt to drop into some container, maybe a trashcan. The idea here is to leave as little work for the HEPA vacuum cleaner as possible. Remember: the vacuum cleaner also uses HEPA. And the more particulates it sucks in, the more frequently you’ll replace it. Or the sooner you’ll wash it if it’s washable.

Step 6

Grab the vacuum cleaner and move its attachment over the filter to blow the dust and debris out. Be sure not to have the end of the cleaner too close to the filter, otherwise, you may end up pulling some of fibers. And that’d reduce the HEPA filter’s air cleaning ability.

Step 7

Get the cleaned filter back into the unit and carry it inside. The good things is that all standalone air purifiers for indoor use are portable. It’s rare to find units weighing over 35 lbs. Besides, most heavy air purifiers have wheels. If the wheels are hidden, you may have difficulty rolling your purifier to the cleaning area, especially if there’s an elevation along the way.  Finally, plug the thing in and start enjoying clean, healthy indoor air.

How Often should you Clean a HEPA filter

Typically, once every 90 days should be fine. But every room’s situation is different. In homes located in areas with higher than average pollution levels, a user must wash their filter more frequently. And if the home is in an area that enjoys pristine mountain air, less cleaning will suffice.

How frequently is too frequently? We saw earlier that vacuuming a HEPA filter may reduce its effectiveness. It may loosen some of the fibers, rendering the filter less portent.  For that reason, avoid over-vacuuming the filter. If the clean filter indicator lights up and the filter doesn’t look dirty, don’t clean it. In some air purifiers, the clean filter indicator is just a timer that tracks calendar days. That means the light comes on after the end of a given number of days. If that’s the kind of indicator you have, ALWAYS remove the filter to see if actually needs cleaning.

Can the Prefilter be Washed?

Yes and no. It depends on the type of prefilter you have. Even if the manufacturer says it’s washable, don’t wash it if it’s made of fibers pretty much like the main filter. But if it looks like some piece of plastic, you can give it a quick rinse under the faucet. Otherwise, vacuum it.

Carbon Filters be Washed?

If you have your air purifier in the basement to tackle basement smells, you want the odor filter working efficiently the whole time.  In some models the odor filter can be cleaned and reused. However, it’s unlikely that the best basement air purifier uses washable activated filter.  If you wash it or use an air compressor on it, you may end up destroying some of the micropores in the filter. And that’d make it less effective, and all those basement VOCs could end up in your bloodstream. I believe it’s best to just replace the activated carbon filter when it’s dirty.

Wrapping it Up

Yes, you can clean HEPA filters. However, washing them or air-compressing them  ruins them. Tests show that vacuuming is the best option you have to boost your filter’s longevity.

Do the cleaning job outside as opposed to indoors. Allergens and other pollutants belong outside of your home. Once you’ve cleaned your filter, click it back into place and move the machine back inside.

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