I have a couple of respirators that I use occasionally for DIY projects. They are pretty lightly used, with only a handful of hours of use each. With the consensus seeming to swing toward wearing masks in public spaces as a preventative measure, I am wondering if one or both of these respirators would be as good as or better than a N95 mask.
One respirator has cartridges rated “GME-P100”. From what I have read these cartridges are significantly better than N95 masks.
The other has cartridges rated “GMA-OV”. This seems to be a rating for organic volatiles but no particle rating. They have pleated pre-filters made of some fragile fabric, but unfortunately I tore one of the pre-filters while trying to vacuum dust from it.
Are either of these respirators useful against Covid-19 aerosol transmission?
The P100 would be an excellent choice: it filters >99.7% of particles vs the 95% in the N95 (P series filters continue to work around oily vapors, while N series are not rated for hydrocarbon exposure).
Some OV filters also have particulate filters in them - sounds like this one may not…so… not so useful in this case.
The problem with the re-usable respirators is that while out and about and exposed to the virus the outside of the mask will become contaminated. If you don’t carefully remove the mask then you could contaminate your hands and face while doing so. You will also need to sanitize the mask exterior, including the straps.
These are not insurmountable obstacles, but it is something to keep in mind.
Air filters capture particles via a number of physical phenomena. Most folks think of filters stopping particles in the same way that the screen mesh in your windows stops insects, but that’s not true. If air passages in the filter were small enough to block particles of interest, you wouldn’t be able to move enough air through them to breathe. Instead, the filter fibers are “sticky” on a molecular level and rely on particles running into them and getting stuck. Very large particles can’t follow the flow around the filter fibers and slam into them like a car on bald tires in the rain. Very small particles are driven toward the filter fibers by diffusion and electrostatic attraction. It turns out that there is a size of particles that is most difficult to capture: about 0.3 microns (300 nanometers). These are the ones that are light enough to follow the flow around the filters, and heavy enough to not be strongly influenced by diffusion and electrostatic attraction. And so this is the particle size that is used when filters are tested for certification.
The upshot of all this is that a filter rated “N95” stops 95% of 0.3-micron particles, but it also stops a far greater percentage of particles at larger AND smaller sizes. If you have a distribution of particle sizes, the total mass getting through an N95 filter is going to be a lot less than 5%.
Likewise, a filter rated N100 or P100 stops 99.97% of 0.3-micron particles, but does much better at other sizes; if you have a distribution of particle sizes, the total mass getting through is going to be a lot less than 0.01%.
