Wood Pellet Risks
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Wood pellets are quite safe to burn, but stored wood pellets are chemically active and can emit dangerous amounts of carbon monoxide.
Wood pellets have grown in popularity in recent years as a source of heat in pellet stoves and pellet boilers. While they are considered a safer and more efficient source of energy than wood, there are some dangers involved, particularly in the storage of wood pellets.
How Wood Pellets Are Made
Wood pellets are made of compressed scrap material and waste from lumber mills. This material includes sawdust, wood chips, and scrap pieces from wood products and construction sites. Pellets may vary slightly in size from 3/8 to 1 inch in length. The material first goes through a hammer mill, a machine that breaks the scrap pieces down into a consistent size. The scrap pieces are then dried, pressed together into pellets under high pressure, cooled and prepared for shipping.
While wood stoves emit large amounts of pollutants, wood pellet stoves burn with better efficiency and produce far less air pollution. A wood stove must be properly vented through a chimney or flue because of the risk of carbon monoxide poisoning. Pellet stoves, on the other hand, burn so cleanly that they often can be direct vented, eliminating the need for a chimney and greatly reducing the chance of carbon monoxide poisoning.
Wood Pellet Boilers
Wood pellets are most often used in pellet stoves, but pellet boilers are gaining in popularity, particularly in Europe. Pellet boilers require a little more work than oil and gas boilers but are seen as less expensive and better for the environment. On a pellet boiler, pellets are fed to the burner from an attached hopper or storage bin, much like an oil-fired boiler is fed from an oil tank.
Barbecue Wood Pellets
Wood pellets are also being used in barbecues and smokers. However, heating pellets should not be used for barbecues. Food-grade pellets are made from hardwood, they're kiln-dried and they burn cleaner. There are several flavors of barbecue pellets, including apple and cherry, with the flavor referring to the type of wood used to make the pellets.
The Dangers of Wood Pellet Storage
It is clear that pellet stoves operate cleanly and efficiently, with far less risk of carbon monoxide poisoning than a wood stove. But with wood pellets, the danger is in storage. When wood pellets are stored, a chemical reaction that produces large amounts of carbon monoxide gas can occur. Carbon monoxide is odorless and tasteless and can be fatal. For this reason, wood pellets should never be kept inside a home. Instead, they should be stored in a separate ventilated structure outside the home.
Always have a carbon monoxide detector in the home when using wood or wood pellets, and post signs about carbon monoxide dangers outside the storage area.
Improper ventilation in a wood pellet storage area can lead to carbon monoxide poisoning.
Gary Sprague is a retired master plumber who started as an apprentice right out of high school and spent over 25 years in the family business. Most of his experience is in residential service and repair work, though he has also worked on new construction and commercial projects.