I've just unearthed my last few face masks. I've had them several years. They are valved, and printed on the front it says "FFP2 822 EN149 2001 JSP". OK, so I google for FFP2, and I see that all three categories of FFP masks, 1, 2 and 3, are described in terms of their suitability for use in progressively increasing Occupational Exposure Limits and Assigned Protection Factors. Descriptions also contain the phrase "They filter at least X % of the particles measuring up to 0.6 µm" where X is either 80, 94 or 99, depending on the FFP number.
It's the bit "up to 0.6 µm" that confuses me. Does it really mean they filter particles from 0.0 µm to 0.6 µm, as it implies? That would make them impermeable even to gas molecules! Or should it read "down to 0.6 µm", as would seem more sensible, i.e. some particles finer that 0.6 µm will get through? If the former, "up to 0.6 µm", I don't see the point of quoting an upper size, as, like I said in an earlier thread, if they filter stuff finer than 0.6 µm, they will filter bricks.