Indoor air pollution has been listed as one of the top five threats to public health. Chemicals are released into the air through a number of catalysts (and often undetected as health threats) including upholstery, curtains, plywood, particle board, stains and varnished, paints, paper towels, tissues, carpets, permanent-press clothing, fabrics, construction materials, modern synthetic furniture, computers, electrical equipment, and cleaning products, and synthetic materials.