Has far as I know no respirator (Other than a full space suit) would
be rated by a manufacturer for use with a beard.
Now that we have the legalities out of the way. A couple of thoughts
No non-positive pressure mask is 100% effective all the time, there
are always small leaks as the person moves their face and has the
rubber ages. This is why Positive pressure masks are used for real
Cheapest, smear a thick layer of Vaseline on the sealing edges of
the mask and you will get an effective seal if the straps are tight.
A method from out in left field usable if he doesn’t have to cast
too often, Get him a nose clip, a Scuba tank and regulator. .
now if your assistant doesn’t like washing up after, or a scuba
tank, then the next type that would work would be a positive pressure
mask. Not cheap but effective, and is what most professional
sandblasters use to protect from the same silica you are trying to
protect against. There are some that only cover the mouth and nose,
so he could still wear his glasses
That’s what should work and keep the nasty dust 99.99% out off his
If you are willing to settle for less than that then any mask with a
rubber seal on tight should do.
The paper masks never seal 100% so that being said and the fact a
lot of people use them (or no mask), I think your hubby should be
safe. And you can both enjoy his facial fur
Just my politically incorrect 2 Cents worth
PS Just remember for any toxin or irritant the danger is
proportional to toxicity, time, concentration and frequency. The risk
for a person casting 2 or 3 times a month, a small batch, and wearing
a mask that is 50% effective is better off than the guy Casting 6
batches a day 5 days a week and doing 100 flasks with a mask that is