Which two factors affect how wood reacts to fire conditions?

• A. Size and moisture
• B. Density and color
• C. Grain orientation and moisture
• D. Size and density

Answer: (A)

Wood's behavior in a fire is governed by moisture content and the size of the piece. Moisture must be boiled away before the wood can pyrolyze and ignite, so wet wood resists ignition and burns more slowly until it dries and the heat can drive off the water. The size of the piece matters because heat must penetrate from the surface to the interior; larger pieces have more mass and heat must travel farther, affecting how quickly they ignite, char, and contribute to flame spread. Color is not a reliable indicator of fire behavior, grain orientation has a lesser influence in this basic context, and density affects heat absorption but doesn’t define fire behavior as directly as moisture and size.