Thanks, Joe. Taking them off and decontaminating them also presents a risk. Respirators and other personal protective equipment can help, but are not foolproof.
I use a dual cartridge (R-61-P100) at work, because I need to cut down on some of the lung irritants I am exposed to. I work in a microenvironment (lab) on wellsite which after years was beginning to have a notoceable short-term effect on my lungs. (fine rock dust, petroleum vapors, and combustion byproducts/flue gasses from the gas detection equipment, and when the wind was wrong, exhaust from the diesels on the drilling rig--High SO2 off-road use diesel exhaust).
One day's worth of beard renders a respirator largely ineffective--in a chemical/fine particulate environment.
A five-O'clock shadow might be enough to cause exposure to a biological through leakage, so everyone who has to shave better add lots of razor blades to their list as well...