[ThePythonicCow]

I presume that a conventional industrial respirator would suffice

I doubt it. Someone infected (perhaps not knowing it yet) with a virus is like a walking cloud of virii. If you get within 3 feet of them or their wake, you need a filter that will stop almost all particles down to .3 micron or some such. Are the industrial respirators you mention able to do this? If not, they're useless.

[steve86]

Yes, the N95 class of mask/respirator is considered adequate vis-a-vis particle size. The 95 refers to 95% stoppage at a target size. It all comes down to mask fit and handling. The metal strip at the top of most masks has to be formed properly to fit the nasal bridge of an individual. Beards can't be present (not a problem for 50% here). Removing and disposal of the mask has to be done extremely carefully. One of the most important benefits of a mask is it stops you from touching your face.

[blam]

The N95 masks are rated to stop 95% of the particles .3 microns or larger. Most virus is .15 micron or smaller.