Can HEPA Filters Be Used to Make DIY Face Masks?

HEPA Filters Effective DIY Surgical Face Mask Coronavirus

HEPA filters have been mentioned as a possible fabric material for making DIY face masks. There are even YouTube videos showing how to DIY a mask out of a HEPA filter.

DIY Face Mask Filter with HEPA Fabric

But just how well can HEPA filters capture virus-sized particles, and can HEPA filters be used to make an actual face mask? In this article, we’ll get to the bottom of whether HEPA filters make effective homemade face masks.

Let’s break this question down into 3 parts:

What are HEPA Filters Made From?

HEPAs are air filters traditionally used in air purifiers or central air systems to clean indoor air. They’re made from a mat of randomly aligned fibers – either polypropylene (PP) or fiberglass. Polypropylene is similar to the material in a sports t-shirt. Fiberglass  Here’s a closeup of the HEPA filter Smart Air makes for The Sqair air purifier, it’s made from PP.

Closeup HEPA filter material

Read more: What exactly are HEPA filters and how do they work »

How Well can HEPA Filters Capture Virus-sized Particles?

Previous studies have shown that HEPAs work great at capturing viruses. In our DIY mask tests, we tested a H11 filter, and found it filtered out over 95% of the most difficult particles to capture.

Testing effectiveness of HEPA filter material at capturing virus-sized particles

Read more: Can HEPA filters actually capture viruses? »

That’s great! The H11 HEPA filter we tested was able to filter out the same percentage of virus-sized particles as an N95. On the surface, HEPA filters might seem like a perfect material to use for masks, but there’s more to it than just particle capture effectiveness.

Will HEPA Filters Make Effective Face Masks?

To answer this question, we need to look at more than just the effectiveness of HEPA filters at capturing viruses. It’s important to consider how easy it is to breathe through a HEPA filter mask. Also, we should consider the health risks from having HEPA filters close to the face and mouth. Finally, can HEPA filters actually be shaped into a well-fitting homemade face mask?

Breathability of HEPA Filter Face Masks

Breathability is important. If we can’t breathe through the mask, it’ll be uncomfortable to wear and we’ll likely take it off. The good news is that in Smart Air’s tests of over 30 DIY materials, the HEPA filter came out as one of the most breathable materials out there. The HEPA filter was about as breathable as a cotton t-shirt.

DIY Mask Breathability of HEPA filter for face mask

Is it Safe to put HEPA Filters so Close to the Face?

Data shows that HEPA filters can shed an insignificant number of tiny fibers when used in air purifiers. The number of fibers shed from HEPA filters are far fewer than the number of tiny PM2.5 particles in the air we normally breathe. In fact, the WHO PM2.5 limit is 35x more than from filter shedding.

number of fibers shed from HEPA filters much less than what we normally breathe

Still, the tiny fibers may still be harmful to our health. Studies are inconclusive, but a group of physicians in the US came to the conclusion that glass fibers like those used in HEPA filters should be considered ‘nuisance dust’, and do not lead to permanent damage.

Read more: Can fibers break off from HEPA filters, and are they harmful to health? »

How Well can a HEPA Filter be Turned Into a Mask?

OK, so we know that HEPA filters are breathable and their impact to health may be limited. That’s great! But how well can we actually make a mask out of HEPA filters. Synthetic polypropylene HEPA filters are made from two parts: the non-woven, particle capturing part, and a stiff PET backing to give the filter its rigidity.

HEPA Filters Made from PET and PP Material Fabric

This stiff PET backing layer makes synthetic filters difficult to fold and and shape. Fiberglass filters are also brittle by nature, since they’re made from glass fibers.


Finally, almost all HEPA filters available on the market are folded into a pleated HEPA design. That gives them better performance when used in air purifiers. Unfolding your HEPA filter may well cause destructive damage to the filter, making it less efficient at capturing viruses.

 

Breaking pleated HEPA filter for DIY face mask may damage fabric material

 


Bottom Line on Homemade DIY Face Masks Made Using HEPA air Filters

HEPA filters are highly effective at capturing viruses, and also breathable too. An insignificant number of small fibers may break off the filters, but they are unlikely to cause permanent damage to health. Synthetic filters are fairly rigid and difficult to shape, whereas fiberglass filters are too brittle. Making masks out of HEPA filters is possible, but not easy to get right.


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Valinor

Very helpfull, learned alot reading your blog.
Personally fibers breaking off so close to my face is something I rather not risk.

Seeing as you guys test alot of materials, do you maybe have like an indication how european en14683 type 2 masks perform.
Their BFE percentage is >98% but unlike US ASTM, testing the PFE value is not necessary and its really hard to find out.
(Currently trying to get it from a few european manufacturers but it seems they are rather more interrested in who I work for than answering y simple question)

Ulli

Thank you for your blog. I read your artices with great interest. I May i bring your attention to evolon CR as material for DIY masks. Like the hepa filter it should block small partikels. It is very breathable (a lot more then op masks), With it’s micro-filamented structure it dont shed respirable particles and at it is used as packing material it is cheap (relative). It can be washed with temperatures up to 95 degrees. For me this sound very good and easier as unfold a filter

Liz - Smart Air

Hi Ulli, Liz here. We haven’t tested evolon yet. We know there’s a huge demand for reliable, science-backed data right now, so we’ve created a campaign to gather information on what our readers want to test. To vote on what test you expect to see and support our campaign, visit our Fundly.com page here: https://fundly.com/best-diy-mask-materials

Audrey Jeffery

This was very helpful, thank you.
Have you tried vacuum cleaner bags?
There are a variety of bags, including those that are supposed to keep allergens in the bag.

Thanks, again,

audrey