The sieving action of facial hair

The Times (in 1853) on why construction workers shouldn't shave (TimesArchive via Marc Abrahams):

I'll transcribe part of it for searchability:

... the London masons are now growing their beards pretty generally, that the fashion is gaining ground, and will soon, in all probability, become universal. The simple action of the moustache in such case is that of a respirator, or, more correctly speaking, a species of sieve, for intercepting the passage of the dust. Besides the respirator having the effect of keeping the lungs clear of foreign particles, it also has the great advantage of preserving a steady and equable warmth around the orifice of the air passages.

I wonder what fraction of these would serve the purpose.