Uh.....what planes are you on where you, the passenger, can simply "pull down the oxygen mask"? Also, wouldn't the P95 only help with particulates (e.g. soot), but not with the actual toxic fumes?
OP has no idea what he's talking about. Passengers masks are for depressurisation events and oxygen supplies last 15 minutes - enough time for the pilots to descend. Pilots have a separate longer lasting oxygen supply. In many (most older?) planes, a single passenger activating their mask will activate the chemical based oxygen supply that feeds all passenger masks.
3M 8577 has a bonus carbon layer for this purpose. Its protection is not complete, but can limit the damage. You should also carry spares in case the carbon layer is exhausted.
