Being able to quickly don a filter mask while you evacuate an affected area is important if not critical.
We are not talking about"Gas masks", they are used for other things, war and police actions require the user to operate while being exposed to Chemical weapons or Nuclear and Biological agents. You will not need to expose yourself to such duties. Your duty is to remove yourself from the effected area and maybe help others while on your way.
Filter classifications:
N95 will filter out 95% of particulate matter.
N99 will filter out 99% of particulate matter
N100 will filter out 99.97% of particulate matter.
Don't buy or carry any mask with less then a N95 rating.
Some filter masks contain small (thin) amounts of activated carbon, and may provide higher degrees of protection from foul odors, smoke, cleaning fumes, toxic chemicals even hanta virus.
These are commercially available through emergency equipment supply vendors. These are usually not sold in bulk like other masks and are more expensive but worth it. Better still, an N95 with your paper activated carbon mask over it.
Carrying a filter mask in your pocket, belt pouch or purse is a good idea, it can buy you precious time to escape a building, aircraft, subway or anyplace the air is against you.
Watch your six
RJ