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Rule of Thumb 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.