I used to use a Dustfoe 88 mask in the shop. A fairly good amount of dust
got through, but I thought anything more would be too hard to breathe
through. I got a headache when doing some extended finishing in the
finishing room in a different building, so I bought a respirator mask for
$20 rated for paints & varnishes. Amazingly, you can't smell the finish at
all through the mask and it is not that hard for me to breathe through. I
decided to try the same mask in my shop for sanding and when applying CA and
it works great. One advantage of the twin cartridge respirator is that I
actually have better field of vision down and ahead than with the other
mask. When you sand the CA you should use a fan to clear the immediate air.
If you are too close and sand too hard you can feel the sting of CA in your
eyes.

But some people are tough enough that they don't need to use safety
equipment with toxic substances (until their liver can handle no more and
they get cancer, etc).