When masks were in short supply during the Covid-19 pandemic, people started questioning whether N95 face masks expire. Are expired face masks (but otherwise untouched) still effective? Surprising results from a peer-reviewed study have led some to question N95 expiration dates.
Do Face Masks Expire?
The answer is yes if you’re talking about disposable masks. Disposable face masks will have a best-by date on the packaging, just like food. While this period is likely to be several years away, it is important to use the masks before then to get the best protection.
Reusable face masks are washable and safe to reuse, making them an excellent choice to stock up on. For the best results, wash the masks according to the instructions on the package and hang them to dry.
Do N95 Face Masks Expire?
Researchers at the University of North Carolina and the EPA tested brand new and 10-year-old expired 3M N95 face masks. The oldest masks had expired 11 years before the study. And if the expiration lifespan is 5 years, that means the oldest masks were 16 years old.
Importantly, the researchers tested the masks on real people’s faces, rather than manikins. These fit tests are important because they take into account the part that people most suspect would degrade–the straps and other pieces that influence fit.
Fit tests compare the number of particles inside the mask while a person is wearing it versus the number of particles outside the mask. In this study, the average particle size was tiny–0.05 microns.
10-Year-Old Expired N95 Masks as Effective as New
Surprisingly, the expired N95 masks were within one percent as effective as the brand-new masks–essentially indistinguishable.
It’s important to note that this was a small study. The researchers tested two different models of expired masks with three masks for each model.
N95 Masks Have Longer Shelf Life Than We Once Thought
However, there is other data suggesting that N95 masks last longer than some people have thought. Our longevity tests found less than a 1% decrease in fit effectiveness in pollution masks worn every day for 30 days.
Read More: How Long Do N95 Masks Last?
Why Do Masks Have Expiration Dates?
Manufacturers mark their masks with expiration dates. For example, 3M says their masks have a 5-year shelf-life when the respirators are stored in their original packing and proper climate conditions (-4F to 86F, not exceeding 80% RH). That leads some to conclude that masks are less effective after this date.
The motivation behind the expiration date is that mask effectiveness depends on having a good fit. Over time, the elastic bands and nose pieces can degrade. If the straps and other structural pieces degrade, the masks will fit less well.
Fit tests found less than a 1% difference in effectiveness between 10-year-old expired N95 masks and brand new masks.
WHAT NEXT?
Along with wearing masks, air purifiers with HEPA filters are also one of the best ways to stay safe from a variety of pollutants in our air including viruses and dangerous PM2.5. A CDC study found lower COVID-19 infection rates in schools that used HEPA air purifiers. HEPA filters can significantly lower the risk of a variety of deadly diseases including diabetes, heart disease, cancer, and high blood pressure.
Read More: Four Steps to Choosing the Best Air Purifier
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