Sanitizing Masks With Alcohol Degrades Performance

With mask shortages during the coronavirus outbreak, some doctors are sanitizing masks with alcohol so they can re-use them. But this raises questions about whether alcohol actually works and whether it degrades the masks.

doctors sanitizing masks with alcohol

 

Does Alcohol Kill Viruses?

The research on alcohol is clear. Alcohol kills viruses. Technically, viruses aren’t alive, so scientists focus on whether the virus is “deactivated” or no longer able to infect humans.

sanitizing plane virus

For example, a 2018 article summarized 17 studies where scientists put alcohol on people’s hands and measured the reduction in virus. Alcohol deactivated over 90% of viruses like the polio virus in most cases, depending on the dose and the particular virus.

sanitizing surface alcohol

However, in 23% of the trials, the alcohol deactivated less than 90% of the virus. Thus, alcohol does “kill” viruses, but not all of them all of the time.

Does Sanitizing Masks with Alcohol Degrade Masks? 

But before doctors can start spraying masks with alcohol, we need to know whether the alcohol degrades the masks. Even a “successful” disinfection is useless if it harms the mask.

Fortunately, scientists have tested this question already. Researchers at the National Institute for Occupational Safety and Health tested N95 masks before and after dipping them in rubbing alcohol (isopropanol). Then they dried the masks overnight.

After the alcohol disinfection, the masks captured 37% less particulate on average.

sanitizing masks with alcohol harms performance data test N95

Why This Mask Test Overstates The Effect

A 37% drop sounds big, but to be fair, this number exaggerates the overall harm. That’s because they tested the particle sizes that are the most likely to be affected by alcohol treatment.

The researchers tested particles from around 0.05 to 0.40 microns. For comparison, the coronavirus averages 0.125 microns. Of course, many particles in the air are larger than 0.4 microns, including some bacteria and even some viruses.

Size of coronavirus particle pm2.5 and bacteria

 

Why does this size range matter? This range around 0.3 microns is the hardest for masks to capture. This chart shows particle capture rates dipping around 0.3 microns. This chart is for HEPA filters, but masks follow the same pattern, with some small differences.

 

HEPA 0.3 microns most penetrating particle size

 

To boost performance in this critical size range, many masks use fibers that have a static charge. Dipping in alcohol removes this charge.

That’s bad news for particles in this size range, but it also means that alcohol does less harm for capturing particles outside this critical range. For example, when the researchers measured even smaller particles, they found out alcohol sterilization harmed performance by less than 5%.

sanitizing masks with alcohol harms performance

Read more: Bouncing explains why it’s actually easier for masks to capture smaller particles.

Bottom Line:Sanitizing Masks with Alcohol

Alcohol deactivates viruses, but it significantly reduces filtration effectiveness, particularly for particles around 0.3 microns.


 

Better Options Than Sanitizing Masks With Alcohol

This finding is similar to results of washing masks with soap and water, which also harms performance. Instead, research is pointing to UV light and simply drying and waiting as better options for disinfecting masks.

Disinfect N95 mask wash alcohol viruses


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MartinRosenwald

How does this apply to the cheap variety store masks?

Liz - Smart Air

Hi Martin, Liz here. We haven’t tested the alcohol effects on different types of masks. However, judging from what we’ve found so far, using alcohol rubbing wouldn’t be a good idea. There is a simple way to disinfect your mask, you can read this article here: https://smartairfilters.com/en/blog/disinfect-clean-n95-mask-virus-coronavirus/

Doris

Just for a non med. user, could one just spray the n95 with alcohol inside and out and let them dry in hot air

Liz - Smart Air

Hi Doris, we didn’t try just spraying. But here is an article on how we recommend to disinfect your mask: https://smartairfilters.com/en/blog/disinfect-clean-n95-mask-virus-coronavirus/

Wayne Keinanen

I spray my lone N95 with a 99.9 % Ethel Alcohol spray – Hopefully it’s still effective to go grocery shopping – but it does remove doors- I also leave it in my truck where it receives the Light if the sun ~ which I believe assists in the decontamination process

Any comments would be appreciated

Dr vaishali

For how many time we must use N95 mask after disinfecting

We’re yet to run tests on how many times you can disinfect N95 masks with alcohol. However, the data in this article shows that disinfecting masks with alcohol can reduce their performance at capturing virus-sized particles around 5%. Based on this, you can decide when you think it’s safest to replace your mask!

Ivan S. Jayawan

Hello Thomas, another way they are talking about sanitizing used surgical / N95 mask is with peroxide vapor (https://news.umich.edu/u-m-engineers-work-to-disinfect-n95-masks-for-frontline-medical-personnel/). I believe CDC has also summarized on the method you can use to sanitize N95 mask (https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html). This is still a great article nevertheless! Cheers!