Formaldehyde is a colorless and easily soluble irritating gas. Particleboard, density board, plywood and other man-made boards, adhesives and wallpaper are the main sources of formaldehyde in the air, with a release period of 3 to 15 years. It can be absorbed through the respiratory tract, and the harm of formaldehyde to the human body has the characteristics of long-term, latent, and hidden. Long term inhalation of formaldehyde can cause serious illnesses such as nasopharyngeal cancer and laryngeal cancer.