Originally Posted by bigabyte
Clean burning means like a campfire basically. A wood fire is a chemical reaction caused when the wood is heated to a high enough temperature that it begins to break down into smaller particles, primarily gasses, and a small amount of solids. If there is enough oxygen present as the gas escapes in this heat, it will ignite causing the flame, otherwise the gases are released in the air unburned (thick smoke). So a clean burning fire is one where the majority of the gasses produced from this chemical reaction are burned up in the heat as opposed to being released into the air, and over your food.
Now that made sense to me...