The 3M™ Ethylene Oxide Monitor 3551 uses the proven scientific principle of diffusion, which is the gradual mixing of molecules of two or more substances. It is designed for sampling personal exposures or work areas in the pharmaceutical, health care and chemical industries. Analysis procedure is available upon request. The monitor utilizes brominated carbon to collect and convert the reactive ethylene oxide to a more stable chemical derivative called 2-bromoethanol. This compound is then desorbed with methylene chloride in methanol. It meets OSHA's requirement for accuracy within +-25% for 8 hour samplings at 1 ppm and the requirement for accuracy within +-35% for 8 hour samplings at the 0.5 ppm action limit. 18 month shelf life.