The service life of organic vapour cartridges varies greatly and depends on the concentration of the contaminants, their physicochemical characteristics (e.g., boiling point, polarity) as well as the characteristics of the charcoal in the cartridge. In addition, other factors such as breathing rate, humidity and temperature affect cartridge service life. The computer-based tool was developed to estimate the service life of cartridges exposed to one or more organic vapours. The objective is to help occupational health professionals determine a cartridge replacement sequence in the context of a respiratory protection program.