室内空气中的甲醛主要来源于装修材料及新的组合家具使用的人造木板，如胶合板、大心板、中纤板、创花板(碎料板)中的粘合剂。遇热、潮解时，粘合剂中甲醛就释放出来。用做房屋防热、御寒的绝缘材料—池沫，在光和热的作用下，老化后也可释放出甲醛。用甲醛做防腐剂的涂料、化纤地毯、化妆品、地板胶等产品，也可缓慢释放甲醛。每支香烟的烟雾中也含甲醛20-88微克。此外，还有少量甲醛来自室外的工业废气、汽车尾气及光化学烟等。
Formaldehyde in the indoor air mainly comes from the wood-based boards used in decoration materials and new combined furniture, such as the adhesives in plywood, big core board, medium fiber board and creative flower board (chipboard). In case of heat and deliquescence, formaldehyde in the adhesive will be released. Pool foam, an insulating material used for house heat and cold protection, can also release formaldehyde after aging under the action of light and heat. Formaldehyde can also be slowly released from coatings, fiber carpets, cosmetics, floor adhesives and other products with formaldehyde as preservative. The smoke of each cigarette also contains 20-88 micrograms of formaldehyde. In addition, a small amount of formaldehyde comes from outdoor industrial exhaust, automobile exhaust and photochemical smoke.