Formaldehyde is a colorless, irritating and easily soluble gas in water. It has the effect of coagulating protein, and its 35%-40% aqueous solution is known as formalin, which is often used as a solution for dipping specimens. Formaldehyde is a highly toxic substance, and formaldehyde ranks second in the priority list of toxic chemicals in my country.
Formaldehyde in the indoor environment can be roughly divided into two categories from its source:
1. Pollution from outdoor air
Industrial waste gas, automobile exhaust, photochemical smog, etc. can emit or produce a certain amount of formaldehyde to a certain extent, but the content of this part is very small. According to relevant reports, the annual average concentration of formaldehyde in urban air is about 0.005~0.01mg/m3, and generally does not exceed 0.03mg/m3. This part of the gas can enter the room at some time and constitute a source of indoor formaldehyde pollution.
2. Pollution from indoor decoration materials
Various man-made boards currently on the market, such as particleboard, medium density fiberboard, and plywood, all use resin with formaldehyde as the main component as a binder, so formaldehyde is inevitably contained;
Adhesives are used in furniture making, wall and floor decoration auxiliary equipment, so wherever adhesives are used, formaldehyde gas will always be released, which will cause harm to the indoor environment;
Small amounts of formaldehyde may remain in paint for decoration and putty used in interior wall painting;
Wallpapers, carpets and new car decoration materials may contain formaldehyde pollution;
Because the urea-formaldehyde foam resin thermal insulation material made of urea-formaldehyde resin has a good thermal insulation effect, it is often made into the building envelope so that the indoor temperature is not affected by the outdoor;
Therefore, in general, the source of formaldehyde in the indoor environment is still very extensive. Generally, the content of formaldehyde in newly decorated houses can reach 0.40mg/m3, and it may reach 1.50mg/m3 in some cases. Studies have shown that the content of formaldehyde in the indoor environment is closely related to the use time, temperature, humidity and ventilation of the house. In general, the longer the house is used, the less formaldehyde remains in the indoor environment; the higher the temperature, the greater the humidity, which is more conducive to the release of formaldehyde; the better the ventilation conditions, the release of formaldehyde in construction and decoration materials Correspondingly, the faster, the more conducive to the cleaning of the indoor environment.
3, the emission route of formaldehyde
1) The wood itself emits a very small amount of formaldehyde under the action of temperature and humidity.
2) In the glue making process, urea-formaldehyde resin will inevitably remain a part of free formaldehyde and emit outwards.
3) During the curing process of the wood-based panel, a part of the linear resin does not form a network structure and is decomposed into free formaldehyde to emit to the outside world.
4) The partially cured resin decomposes under the action of heat and moisture to form free formaldehyde and emit outwards.
Japanese research shows that the release period of formaldehyde from indoor wood-based panels is generally 3 to 15 years.