The certificate indicates that while the mask does often provide >99% filtration, there are times when it drops as low as 97%. While 97% fine particle filtration is still a good result, it is less than the 99% that is advertised.
The certificate indicates that while the mask does often provide >99% filtration, there are times when it drops as low as 97%. While 97% fine particle filtration is still a good result, it is less than the 99% that is advertised.