What is It?

Formaldehyde is a colorless, strong-smelling gas. It is widely used to manufacture building materials and numerous household products. Its most significant use in homes is as an adhesive resin in pressed wood products. It is one of the large family of chemical compounds called volatile organic compounds or “VOCs.” The term volatile means that the compounds vaporize, that is, become a gas, at normal room temperatures.

There are two types of formaldehyde resins: urea formaldehyde (UF) and phenol formaldehyde (PF). Products made of urea formaldehyde release formaldehyde gas; products made of phenol formaldehyde generally emit lower levels of the gas.

Where is Formaldehyde Found?

Formaldehyde is an important industrial chemical used to make other chemicals, building materials, and household products. It is used in glues, wood products, preservatives, permanent press fabrics, paper product coatings, and certain insulation materials. Building products made with formaldehyde resins can “off-gas” or emit formaldehyde gas. These products include particle board used as sub-flooring or shelving, fiberboard in cabinets and furniture, plywood wall panels, and foamed-in-place urea formaldehyde insulation. Incomplete combustion; cigarette smoking; and burning wood, kerosene, and natural gas also release formaldehyde.

What Affects Formaldehyde Levels?

Formaldehyde levels in the indoor air depend mainly on what is releasing the formaldehyde (the source), and the temperature, humidity, and air exchange rate (the amount of outdoor air entering or leaving the indoor area). Increasing the flow of outdoor air to the inside decreases the formaldehyde levels. Decreasing this flow of outdoor air by sealing the residence or office increases the formaldehyde level in the indoor air.

As temperature rises, more formaldehyde comes off the product. The reverse is also true—less formaldehyde comes off at lower temperatures. Humidity also affects the release of formaldehyde from the product. As humidity rises, more formaldehyde is released.

The formaldehyde levels in a residence change with the season and from day-to-day and day-to-night. Levels may be high on a hot, humid day and low on a cool, dry day. Understanding these factors is important when you consider measuring the levels of formaldehyde.

Only trained professionals should measure formaldehyde because they know how to measure accurately and interpret the results. As mentioned earlier, many factors can affect the level of formaldehyde on a given day in a home. That is why a professional is best suited to make an accurate measurement of the levels if a measurement is required.

Formaldehyde is normally present at low levels, usually less than 0.06 ppm (parts per million), in both outdoor and indoor air. Average concentrations in older homes without urea formaldehyde foam insulation (UFFI), are generally well below 0.1 ppm. In homes with significant amounts of new pressed wood products, levels can be greater than 0.3 ppm.

What Are the Health Effects?

Formaldehyde can affect people differently. Some people are very sensitive to formaldehyde, while others may not have a noticeable reaction to the same level. Everyday, you probably use many products that contain formaldehyde. You may not be able to avoid coming in contact with some formaldehyde in your normal daily routine.

If formaldehyde is present in the air at levels at or above 0.1 ppm, acute health effects can occur. Reactions include watery eyes; burning sensations in the eyes, nose, and throat; nausea; coughing; chest tightness; wheezing; skin rashes, and other irritating effects. Sensitive people can experience symptoms at levels below 0.1 ppm. One problem in identifying the trigger is the fact that colds, flu, and allergies as well as other gases present indoors can cause symptoms similar to some of those produced by exposure to formaldehyde. “Formaldehyde has caused cancer in laboratory animals and may cause cancer in humans” (CPSC). It may also cause headaches and loss of coordination.

Persons have been known to develop allergic reactions to formaldehyde through skin contact with solutions of formaldehyde or durable-press clothing containing formaldehyde. Others have developed asthmatic reactions and skin rashes from exposure to formaldehyde.

Steps to Reduce Exposure

  • Use pressed wood products labeled as low-emitting or products made from phenol resins, not urea resins, such as oriented strand board or softwood plywood.
  • Use air conditioning and dehumidifiers to maintain a moderate temperature and to reduce humidity levels (30 to 50 percent).
  • Increase ventilation, particularly after bringing new sources of formaldehyde into the home. Overall levels of formaldehyde can be lower if you increase the ventilation over an extended period.
  • Use alternative products such as lumber, metal, or solid wood furniture.
  • Avoid the use of foamed-in-place insulation containing formaldehyde, especially urea formaldehyde foam insulation.
  • Wash durable-press fabrics before use.
  • Enclose unfinished pressed-wood surfaces of furniture, cabinets, or shelving with laminate or water-based sealant. Be sure to seal completely with a material that does not itself contain formaldehyde.
  • Make sure that all combustion sources are properly adjusted and vented correctly.
  • Avoid smoking indoors.
  • Remove from your home the product that is releasing formaldehyde in the indoor air.



  • U.S. Environmental Protection Agency.
  • Environmental Health Center, a division of the National Safety Council.
  • “An Update on Formaldehyde,” U.S. Consumer Product Safety Commission.


Adapted by Janie L. Harris, M.Ed., CRS, former Extension Housing and Environment Specialist, Texas A&M AgriLife Extension Service, Texas A&M System. 1999.


Last updated: July 3, 2015

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