Well, if you quit eating beans, she would not be wearing the gas mask......
Note on filters- the various militaries of the world use a PROTECTIVE Mask- not a Gas Mask. The filters are intended to filter out- solid particles, such as radioactive dust, spores, etc. That is the N and B part of the designation- Nuclear and Biological. The C part- Chemical- depends on the chemical. They are basically an absorbent type filter- combination of charcoal and some chemicals. They will work for chlorine, riot control gasses, mustard, phosgene, nerve agents, choking agents, etc. They will not stop EVERY chemical (ammonia goes right thru everything except an ammonia rated filter) and they DO NOT MAKE OXYGEN- wearing one into an O2 depleted atmosphere is death.
Some military forces also use a Riot Control Agent Mask. Less costly, lighter, easier to breathe through- works for tear gas, but not Nerve Agent, Chlorine, etc.
Filters have a life span- once opened, they begin to lose effectiveness. Beware of British gas masks from back in WW2. They used asbestos in the filters.
And yes, I have respirators, protective masks, and even have a couple of Level A Full Body suits. I teach the OSHA 40 hr HAZWOPER course now and again- and the suits come in handy for Halloween.