3M™ Formaldehyde Air Monitoring System with Prepaid Analysis is designed for personnel or work areas in health care, laboratories and in the chemical, pulp/paper, foundry and textile industries. The monitor uses a bisulfate-impregnated filter and is analyzed by colorimetry. It uses the proven scientific principle of diffusion, which is the gradual mixing of molecules of two or more substances. Monitor has an 18 month shelf life, available as 5 case. Designed to be used for 8 hrs TWA sampling to meet the OSHA requirement of +/-25% accuracy at 0.5 - 5.0 ppm.