Don't Burn Treated Wood
The small scraps of lumber that seem to collect and multiply under back porches and in garages often make their way into wood stoves and fireplaces in the winter months. And, as long as it is dry, any species of wood will burn well. Small pieces of plywood or OSB (oriented strand board, aka “chipboard” or “flakeboard”) can also be burned, providing pleasant warmth and cleaning up a mess in the process.
In contrast, preservative treated wood should not be burned. For many years, the most common preservative mixture used for treated wood was CCA, a combination of chromium, copper and arsenic. When wood treated with this preservative is burned, some of the arsenic is released into the air with the fly ash, and the rest is concentrated in the ash that remains in the fireplace. Newer preservative formulations that do not contain arsenic have largely replaced CCA, but it is still not recommended that they be burned.
Treated wood is often used for decking, railings and exterior trim. The most common types of treated wood are green in color, and thus usually can be easily identified. These materials should go to the landfill along with ordinary household waste. Treated wood that has been outside for a long time may turn grey and can be hard to identify – if there is any doubt as to whether it is treated wood, throw it out. Wood that has been painted also should not be burned.
Some wood species such as cedar, redwood, cypress and black locust are used outside because they naturally contain chemicals which protect them from insect and fungal attack. It is perfectly safe to burn these woods.
Using wood “waste” as a fuel for fires is common in the wood products industry and is perfectly acceptable at home too. Just be sure to put painted and preservative treated wood in the garbage, rather than into the fireplace.