Formaldehyde

• Some pressed-wood products, including hardwood plywood paneling, particleboard and medium density fiberboard, contain adhesives with urea-formaldehyde resins. New pressed-wood products with these resins sometimes release formaldehyde during times of increased indoor temperatures or humidity, causing health effects that include nausea, throat irritation, fatigue and allergic reaction, according to the U.S. Environmental Protection Agency.
  
  

Swelling and Shrinking

• The swelling and shrinking of wood varies primarily because of the moisture content of wood, but temperature changes often affect moisture levels. Wood swells the most during hot, humid temperatures, but a dehumidifier and air conditioner help reduce this swelling. Paneling shrinks during cold, dry seasons, but a humidifier can maintain the wood during these conditions.
  
  

Mold

• Wood primarily consists of the structural polymers cellulose, lignin and hemicellulose, along with several sugars, starches, fatty acids and other biological materials. These materials remain in the wood after harvest, making it a food source for mold fungi. The Western Wood Products Association reports that mold thrives on wood in moist environments between 70 and 85 degrees Fahrenheit.