Respirator exhaust valves.

I have a GVS/Miller P100 respirator that I originally got to deal with hay fever and dust issues while I was mowing. A similarly-bearded friend in CA had recommended that model to me as ‘ good for riding a bicycle through forest fire smoke’. When I got mine, I tested the seal on my bearded face: I can make my ears pop if I cover the exhaust valve. I’ve never seen a non-powered respirator that didn’t have some kind of exhaust valve — and the powered ones still dump your exhaled breath into the space you’re in.

Not wanting to expose other people to my breath, I looked at clamping a filter onto the exhaust port. Some decades ago, I worked in a motorcycle shop. I knew that there were air filters designed to clamp onto individual carburetors — and those carbs came in all sorts of sizes. I did some searching and, as it turns out, I had some options. My choices were pleated paper, pleated fabric, or foam. I was leaning ‘foam’ as those were a tad lighter — and I had concerns about the filter staying on.

Then I had a minor epiphany: I could put the same foam used in those air filters inside the mask, over the valve, large enough that no exhalation could escape without getting filtered. It’s not as effective as exhaling through a no-valve N95 mask, but certainly as good as a couple of layers of cloth in a mask. (Hey, if it can keep dust out of a dirtbike motor…)

Face palm: I had some of that foam on hand; it just hadn’t occurred to me that I could use it until I went through the above mental gyrations. Sigh.

I discussed this with a neighbor who has the same mask. He had had the same concern — and being a woodworker with a pack of 3M ‘nuisance dust’ masks in his shop, discovered that those fit perfectly inside his respirator. I should mention that we both have the GVS Elipse / Miller LPR-100 (made by GVS, marketed by Miller as it fits under a welding helmet. Looks like they’d fit under a face shield as well.