Knowing when to change the cartridge of an air-purifying respirator (APR) is necessary, but it can be tricky. These cartridges, particularly those for gases and vapors, contain sorbent material that has a maximum capacity to trap contaminants. Once the element is “full,” any contaminant in the inhaled air breaks through the cartridge into the facepiece, exposing the user. Obviously, the cartridge must be changed before this occurs. But how can you tell when it’s time to change the filter?
To help you answer that question, OSHA addressed the issue of cartridge service life in the revised respiratory protection standard (29 CFR 1910.134). In addition to creating regulatory guidelines, the agency now provides some helpful tools — both of which will be discussed in this article.