<<Disclaimer: Verify this information before applying it to your situation.>>
 
Note:  This information was current at the time I graduated in 1988.
 
First and foremost:  When using a respirator, you must ensure that the
filter cartridge you are using is approved for use with the chemicals you
are being exposed to.  "Dust and mist" filters are useless for chemicals.
Different chemicals may require different cartridges.
 
A major problem with chemical respirators is that odor is the only way to
tell when the cartridge becomes saturated.
This is acceptable only if  1) the chemical has a detectable odor  and 2)
the amount you must inhale to detect the odor (and then to get to an area
where you can remove the mask!) is small enough to not cause a problem.
If "just a few seconds of fumes"  causes you problems, then you will
probably not be able to rely on the odor to warn you.
 
You can test a cartridge by using a test scent such as isoamyl acetate
("banana oil"):-    Open it outside of the mask - if you can smell it
through the mask the cartridge is saturated (or the mask may not be sealed
properly).   ,If you can't smell the odor, then you know the cartridge is
not saturated but, unfortunately, there is no way of knowing how close to
saturation it is.   It could quit on you at any time.  After you have
tested the mask, sniff the scent without the mask to test your sense of
smell.  If you can't smell anything that day (because of cold, etc.) then
you can't tell if your cartridge becomes saturated.
 
Federal Regulations forbid the use of chemical respirators for protection
from chemicals without "adequate warning properties" (odor).
 
I would strongly recommend that you find out exactly what chemicals you are
being exposed to (the containers are required to be labeled by Federal
Regulations, although, unfortunately, some companies ignore this).  Then
look up those chemicals in a medical library and find out what the symptoms
and effects of exposure are.   It's quite possible that anyone exposed to
them should be using a respirator.