Formaldehyde is a naturally occurring organic compound composed of carbon, hydrogen and oxygen with a simple chemical structure of CH2O. It is a highly reactive and colorless gas with a strong odour small. It has been classified by the International Agency for Research on Cancer (IARC), a divison of the World health organization (WHO) as a carcinogen (Category 1) to humans and animals. Exposure to formaldehyde emissions can leads to various effect especially to health related problems. The most common effects are irritation to the eyes, nose, throat and skin sensitization. It can also increase breathing problem for people with health conditions like asthma. Besides that, long term formaldehyde exposure in high doses can cause chronic toxicity and cancer of nasopharynx and leukemia. According to the IARC, formaldehyde less than 0.1 ppm is undetectable by smell but at concentrations between 0.1 ppm and 0.5 ppm formaldehyde can be detected by the pungent odour, with some sensitive individuals will experience a slight irritation to the eyes, nose and throat. At level between 0.5 to 1.0 ppm, most people will experience sensory irritation (i.e., eyes, nose, and throat), while at higher concentration exposure, usually above 1.0 ppm, it will cause extreme discomfort.

The biggest source of formaldehyde emission is from building materials, paints, insulations and furniture materials. For instance, formaldehyde based resins are used to bind the composite wood products such particleboard, medium density fibreboard and plywood to produce cabinets, flooring materials and wall panels. There are various type of formaldehyde based resin that was used in wood composites depending to the end products but urea formaldehyde resins are the most predominant which covers around 85% of the total worldwide. Urea formaldehyde resins are widely used due to their cost effective, fast curing, water solubility, colorless and ease of use under a wide range of press conditions. However, the biggest downside of urea formaldehyde resins are formaldehyde emission into the environment during curing due to unreacted monomer and long term resin degradation (hydrolysis).

It must also be noted that wood itself is a natural material that contains formaldehyde and can contributes to formaldehyde emission. Formaldehyde in wood can be detetected from the main components of woods such as cellulose, hemicellulose, lignin and extractives. The formaldehyde emission from solid wood increases at elevated and prolonged heating times during wood processing including drying and pressing. However, formaldehyde emissions from wood itself is not expected to be a significant contributor to the total amount of the emissions from composite wood panels.

Many countries around the world have imposed strict regulations and standards regarding formaldehyde emission from wood panels. Therefore, there are four major strategies that have been applied by the industries to minimize the formaldehyde emission such as 1) reduction of formaldehyde content in resin formulation, while attempting to maintain adhesive performance, 2) addition of formaldehyde scavengers to resin or wood particles, having the negative effect of consuming formaldehyde prior to resin cure, 3) implementation of surface treatments after board production, and 4) use of alternative adhesive systems with reduced or no emissions, with an impact on product cost and/or performance.

Carvalho, L., Magalhães, F., & Ferra, J. (2012). Formaldehyde emissions from wood-based panels-Testing methods and industrial perspectives. Formaldehyde: chemistry, applications and role in polymerization, 1-45.

Salem, M. Z. M., & Böhm, M. (2013). Understanding of formaldehyde emissions from solid wood: An overview. BioResources, 8(3), 4775-4790.