Can HEPA Filters Be Used to Make DIY Face Masks?

HEPA Filters Effective DIY Surgical Face Mask Coronavirus

News media like The New York Times and Today have been talking about using HEPA filters as a material to make 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? Let’s break this question down into four simpler questions.

1. Can HEPA Filters Capture Viruses?

Scientists have tested whether HEPA filters capture viruses by shooting viruses at the filters and measuring how many make it through. Those tests have found that HEPAs work great at capturing viruses.

 

HEPA Filters DIY Mask Capture Viruses

 

In our DIY mask tests, we tested a H11 filter, and found it filtered out over 95% of virus-sized particles.

 

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

Read more: Can HEPA filters actually capture viruses? »

That means this H11 HEPA filter was able to filter out at least as much virus-sized particles as N95 masks. From this fact alone, HEPA filters seem like a perfect material to use for masks. However, there’s more to masks than just capturing particles.

2. Are HEPA Filters Breathable?

A critical question for making masks is breathability–how easy it is to breathe through a HEPA filter mask? 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

3. Is It Safe to Put HEPA Filters So Close to The Face?

Another critical question is whether it’s safe to put HEPA fibers next to our face and mouth. Some people have questioned whether fibers from HEPA filters break off, enter people’s lungs, and cause damage.

 

Breathing Hazard Safety

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

Scientists have tracked this with real HEPA filters and found that HEPA filters 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. Researchers have argued for both sides of the question, 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? »

 

4. How Easy Is It to Shape HEPA Filters Into DIY Masks?

OK, so we know that HEPA filters are breathable and their impact to health may be limited. 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. If the HEPA is made from fiberglass, then it will be brittle. That presents a challenge.

Finally, HEPA filters present another challenge: unpleating. Almost all HEPA filters on the market are folded into a pleated HEPA design.

 

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

 

That improves their performance in air purifiers, but makes masking a challenge. Unfolding your HEPA filter may damage the filter, making it less efficient at capturing viruses.


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

HEPA filters are highly effective at capturing viruses and breathable too. An insignificant number of small fibers may break off the filters, but they are unlikely to cause permanent damage to health. Shaping the masks is possible but not easy because synthetic filters are fairly rigid, whereas fiberglass filters are too brittle.


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