How do I know when it's time to change them?
The filters I use have a "use by date on them", when I am not
using them I store the filters in zip-lock plastic bags.
If you are using something like an organic vapor cartridge and not
just a dust filter your cartridges are probably way past any useful
life. These cartridges are meant for a service life of hours or
maybe a day in the environment where they are necessary but that is
There is no quick and easy way to know the useful life of a
respirator cartridge. Contaminate concentration, contaminate
type(s), humidity, breathing rate and several other factors play
into how long a cartridge is good for. But here is a rule of thumb
from the OSHA website that will possibly get you in the ball park.
Experimental work can allow for a generalization or "rule of thumb"
that broadly defines the service life of cartridges exposed to
chemicals. One such Rule of Thumb for estimating organic vapor
cartridge service life is found in chapter 36 of the American
Industrial Hygiene Association (AIHA) publication "The Occupational
Environment - Its Evaluation and Control."
It suggests that:
If the chemical's boiling point is > 70 C and the concentration is
less than 200 ppm you can expect a service life of 8 hours at a
normal work rate.
Service life is inversely proportional to work rate.
Reducing concentration by a factor of 10 will increase service life
by a factor of 5.
Humidity above 85% will reduce service life by 50%
These generalizations should only be used in concert with one of the
other methods of predicting service life for specific contaminants.
James Binnion Metal Arts