If you use an outdoor fire pit, you use wood as your source of fuel to get it roaring. But not all wood is the same, and you should avoid pressure-treated wood. This is lumber that's designed for construction -- railroad ties, decking, shipping pallets –- and it is treated with chemicals to prevent rotting. Those chemicals are released when this wood is burned, and they can be dangerous. If you have some leftover untreated plywood, it's fine to burn. But when in doubt, don't take the risk. Also, avoid burning cardboard: It can create huge, smoldering "flakes" that can travel and ignite fires.
ANDREWS MCMEEL SYNDICATION