Formaldehyde is a colorless, pungent-smelling gas, which can cause watery eyes, burning sensations in the eyes and throat, nausea, and difficulty in breathing in some humans exposed at elevated levels. High concentrations may trigger attacks in people with asthma. There is evidence that some people can develop a sensitivity to formaldehyde.
The National Institute for Occupational Safety and Health (NIOSH) recommended limit for occupational exposure to formaldehyde is 20 ng/L (16ppb), and the World Health Organization (WHO) recommends short-term exposure to not exceed 100 ng/L (80ppb). Many homes have levels that contain 30-70 ng/L, and can be higher with poor ventilation or recent construction.
Sources of formaldehyde in the home include building materials, smoking, household products, and the use of un-vented, fuel-burning appliances, like gas stoves or kerosene space heaters. Formaldehyde is also used in a number of manufactured products. For example, it is used to add permanent-press qualities to clothing and draperies. In the home it is most often found in building materials such as pressed fiberboard (it is found in the adhesives). Formaldehyde emissions will generally decrease as products age. When the products are new, high indoor temperatures or humidity can cause increased release of formaldehyde from these products.
To reduce exposure to formaldehyde emissions you should avoid use of pressed wood products or use exterior grade products, which emit less formaldehyde. You should also maintain a moderate indoor temperature, decrease humidity and have adequate ventilation.