To reduce exposure to formaldehyde off-gassing from engineered wood products, which practice is most effective?

• A. Increase indoor humidity
• B. Seal products with coatings
• C. Increase filtration
• D. Increase outdoor air

Answer: (D)

Formaldehyde off-gassing from engineered wood is a gas that builds up indoors unless it’s diluted or removed. The most effective way to lower exposure is to increase the outdoor air entering the space, which dilutes the indoor concentration and pushes the emitted formaldehyde out of the building. In a well-mixed room, the steady-state concentration is roughly the emission rate divided by the air exchange rate; raising outdoor air increases this exchange rate and lowers the concentration accordingly.

Other options have limitations. Increasing indoor humidity can actually raise emissions from some wood products and isn’t a reliable way to reduce exposure. Sealing products with coatings can reduce emissions on treated surfaces, but it’s impractical to seal everything and won’t address all sources. Filtration may help a bit, especially with activated-carbon systems, but typical filters aren’t as effective for low levels of a gas like formaldehyde and can be limited by capacity.