This is from a dental journal, I have quoted this because it includes something about the US grades, but there is similar information on NHS sites and from the WHO.
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FFP3 face masks are the most effective at filtration, with a minimum filtration of 99% and a maximum leakage of 2% to the inside. These masks are better shaped to your face for a more snug fit and typically have a valve to help breathe as the filtration material is much thicker. The valve also reduces the build up of moisture, lengthening the lifespan of the mask. FFP3 masks are typically used for handling asbestos.
FFP2, FFP3, N95 and other respirator masks are effective at protecting the wearer from viral transmission.
It should be noted that N95 masks can not be officially legally recommended for use in Europe although in the current situation with PPE shortages in practice a more flexible approach seems to be being taken.
What are the US and European Standards for face masks?
Medical masks and respirators undergo different standards and regulations, dependent on the geographical area to which they are manufactured.
Medical masks in Europe must comply with the European standard EN 14683, which have 3 levels of bacterial filtration efficiency (BFE1, BFE2, Type R). In the US medical masks must comply with ASTM standards, which have three levels of protection (from low risk of exposure to fluids to high risk of exposure to fluids).
Respirators in Europe must meet European standard EN 149: 2001, which includes three classes of disposable particulate respirators (FFP1, FFP2 and FFP3). In the US respirators must comply with NIOSH (National Institute for Occupational Safety and Health) standards.
Within this standard, there are several classes of respirators depending on the degree of oil resistance:
- Class N: no oil resistance. A distinction is made between N95, N99 and N100. The number after the letter indicates the percentage of filtration of suspended particles.
- Class R: mask resistant to oil for up to eight hours. Here again, a distinction is made between R95, R99 and R100.
- Class P: a completely oil-resistant mask. There are also P95, P99 and P100."
One important aspect is fitting, there must not be leakage at the edges, the nose being the most dangerous area, I wear glasses and find a good strong exhalation will mist them up if I have not quite got it right.
The other thing I do if I have been anywhere that feels dangerous is use 'First Defence', an antiviral nasal spray.