Knowing the specific contaminant and exposure levels is important to determine the appropriate respirator and cartridge for your work environment. This information will also help in estimating the life of selected 3M™ Cartridges. 3M™ Formaldehyde Monitor 3721+ uses diffusion, rather than a pump, to collect an air sample with an accuracy of +/-25% at a 95% confidence level for certain aldehydes found as workplace contaminants. It has fiberglass coated with 2,4-dinitrophenylhydrazine (DNPH) for easy collection of aldehydes and is typically used in health care, laboratories, and in the chemical, pulp/paper, foundry and textile industries. After following all instructions, send the monitor to be analyzed in the lab of your choice. This monitor has a 1-year shelf life from its production date.