That’s a short question with a long answer. For brevity, we can just say that I’d prefer that money go to businesses which support a traditional retail model, which often include locally-owned small businesses, which often face competition within their niche, rather than supporting a company which isn’t that—because this is (slightly) better for humankind in the long run.
If you disagree . . . well, the request still stands as a request.
Standard p100 filters should be sold anywhere these masks are, so I doubt that would be needed.
It seems that you’re right—if you’ll forgive the n=1 sample size, I can get P100 filters at the same store as the mask. This surprised me, as I’d expect that filters that are fine enough to be effective against viruses would be a separate and more specialized item than the filters which are used for industrial hazardous particle filtration.
Since I was surprised, I’ve done a little more digging. I’d like to hear more about why you expect P100 filters to be effective in a potential pandemic, and how effective you think that they will be.
P100 filters are tested against particles 0.3 microns in diameter. This is the same standard as N95 masks. Compare that to the size of viruses in a table of representative key viruses in a textbook, or the recent coronavirus. Yes, some viruses are big enough to be mechanically filtered; most aren’t. Yet N95 masks are effective against smaller particles down to the size of a typical virus; this is achieved through methods other than mechanical filtration, such as electrostatic attraction. (Notably, under some conditions they become more effective as particle size decreases.) This study has a roughly similar setup for P100 rather than N95 respirators. It isn’t quite an apples-to-apples comparison because the particle type is different. However, it’s noteworthy that (arbitrarily choosing a 100 nm particle, 30 L/min median inspiratory flow, taking the average of the different breaths/min tested) P100 filters do worse by a factor of about 10 than N95! This doesn’t change much if you look at particles down to about 50 nm and up to about 200 nm (which is as high as the second study goes).
Perhaps whatever is done to filters to make them oilproof (which is what the “P” stands for) happens to impair their effectiveness against smaller particles? Maybe it interferes with the aforementioned electrostatic attraction?
Going from n=1 again, the store that stocks P100 filters doesn’t carry N95 filter for that mask. Do you recommend P100 filters rather than N95 due to availability? Since we’re using these filters outside of their rated specifications (we’re interested in smaller particles), this might be a case where bigger numbers aren’t actually better.
this is (slightly) better for humankind in the long run
We don’t have to get into this here if you don’t want to, but flagging that I’m not convinced of this.
It isn’t quite an apples-to-apples comparison … do worse by a factor of about 10
Thanks for looking into this! I am pretty skeptical of studies that don’t explicitly compare the two options, because there are really quite a lot of variables that can go into measuring absolute effectiveness that are nicely factored out when you measure relative effectiveness.
The way it’s supposed to work is that going from n95 to n100 should get you from 95% to 99.97% on the worst performing non-oilborne particle size, and then n100 to p100 would get you coverage for oilborne (which we don’t expect to need for a pandemic, but is useful in industry). But I haven’t looked into studies to verify that it does actually work that way in practice.
That’s a short question with a long answer. For brevity, we can just say that I’d prefer that money go to businesses which support a traditional retail model, which often include locally-owned small businesses, which often face competition within their niche, rather than supporting a company which isn’t that—because this is (slightly) better for humankind in the long run.
If you disagree . . . well, the request still stands as a request.
It seems that you’re right—if you’ll forgive the n=1 sample size, I can get P100 filters at the same store as the mask. This surprised me, as I’d expect that filters that are fine enough to be effective against viruses would be a separate and more specialized item than the filters which are used for industrial hazardous particle filtration.
Since I was surprised, I’ve done a little more digging. I’d like to hear more about why you expect P100 filters to be effective in a potential pandemic, and how effective you think that they will be.
P100 filters are tested against particles 0.3 microns in diameter. This is the same standard as N95 masks. Compare that to the size of viruses in a table of representative key viruses in a textbook, or the recent coronavirus. Yes, some viruses are big enough to be mechanically filtered; most aren’t. Yet N95 masks are effective against smaller particles down to the size of a typical virus; this is achieved through methods other than mechanical filtration, such as electrostatic attraction. (Notably, under some conditions they become more effective as particle size decreases.) This study has a roughly similar setup for P100 rather than N95 respirators. It isn’t quite an apples-to-apples comparison because the particle type is different. However, it’s noteworthy that (arbitrarily choosing a 100 nm particle, 30 L/min median inspiratory flow, taking the average of the different breaths/min tested) P100 filters do worse by a factor of about 10 than N95! This doesn’t change much if you look at particles down to about 50 nm and up to about 200 nm (which is as high as the second study goes).
Perhaps whatever is done to filters to make them oilproof (which is what the “P” stands for) happens to impair their effectiveness against smaller particles? Maybe it interferes with the aforementioned electrostatic attraction?
Going from n=1 again, the store that stocks P100 filters doesn’t carry N95 filter for that mask. Do you recommend P100 filters rather than N95 due to availability? Since we’re using these filters outside of their rated specifications (we’re interested in smaller particles), this might be a case where bigger numbers aren’t actually better.
We don’t have to get into this here if you don’t want to, but flagging that I’m not convinced of this.
Thanks for looking into this! I am pretty skeptical of studies that don’t explicitly compare the two options, because there are really quite a lot of variables that can go into measuring absolute effectiveness that are nicely factored out when you measure relative effectiveness.
The way it’s supposed to work is that going from n95 to n100 should get you from 95% to 99.97% on the worst performing non-oilborne particle size, and then n100 to p100 would get you coverage for oilborne (which we don’t expect to need for a pandemic, but is useful in industry). But I haven’t looked into studies to verify that it does actually work that way in practice.