Wood will give off or take on moisture from the air until the moisture in the wood is balanced with the moisture in the air. This is called _____________.

• A. Hygroscopic equilibrium
• B. Oven-dry moisture content
• C. Moisture balance
• D. Equilibrium moisture content

Answer: (D)

Wood is hygroscopic, so it continually exchanges moisture with the surrounding air until its moisture content matches the environment. The state where the wood stops gaining or losing moisture is called the Equilibrium moisture content. This EMC depends on temperature and relative humidity, so in the same room the wood reaches a stable moisture level that can cause it to swell or shrink as humidity changes. Oven-dry moisture content refers to wood that is completely dry, not the balanced state with the air. A general term like moisture balance isn’t the standard name for this specific condition, and while hygroscopic describes the property, the precise term for the balanced point is Equilibrium moisture content.