Cooler temperatures may mean lighting a fire in the fireplace at home, but to burn the cleanest fire, always use dry wood. Firewood that has not been properly dried out -- or seasoned -- is called "green" or "wet" wood. While it does burn, it doesn't do so completely, and it releases more pollutants into the air and can actually bring smoke into your home. This creates an unhealthy air environment in your home. How can you tell if your firewood is properly seasoned? When it burns, the wood should snap or crackle; wet wood will make a hissing sound.