Smoke forms when wood or other organic matter burns. The smoke from wood burning is made up of a complex mixture of gases and fine particles (also called particle pollution, particulate matter, or PM). In addition to particle pollution, wood smoke contains several toxic harmful air pollutants including: benzene, formaldehyde, acrolein and polycyclic aromatic hydrocarbons (PAHs). The more efficiently you burn wood (e.g., using an EPA-certified wood stove and dry, seasoned wood) the less smoke and pollution is created.
What are the effects of wood smoke?
Smoke may smell good, but it's not good for you. The biggest health threat from smoke is from fine particles, also called fine particulate matter or PM2.5. These microscopic particles can get into your eyes and respiratory system, where they may cause burning eyes, runny nose, and illnesses, such as bronchitis. Fine particles can make asthma symptoms worse and trigger asthma attacks. Fine particles can also trigger heart attacks, stroke, irregular heart rhythms, and heart failure, especially in people who are already at risk for these conditions. Learn more about the health and environmental effects of fine particles.
Who is at risk from wood smoke?
Wood smoke can affect everyone, but children, teenagers, older adults, people with lung disease, including asthma and COPD or people with heart diseases are the most vulnerable. Research indicates that obesity or diabetes may also increase risk. New or expectant mothers may also want to take precautions to protect the health of their babies, because some studies indicate they may be at increased risk.
Types of Wood Burning Appliances
When choosing your wood burning appliance, consider efficiency, emissions, and the size of the space you'll be heating. The cleanest wood-burning and most efficient appliances are marked with EPA-certified and EPA-qualified labels. If you choose to heat your home with wood, use the cleanest wood-burning appliance possible.
Pellet stoves are similar in appearance to wood stoves; however, instead of wood, pellet stoves burn a renewable fuel made of ground, dried wood and other biomass wastes compressed into pellets. Pellet stoves operate by pouring pellets into a hopper which feeds automatically into the stove. Unlike wood stoves and fireplaces, most pellet stoves need electricity to operate. For additional information visit: Summary of Requirements for Wood stoves and Pellet Stoves.
Hydronic Heaters (also called wood boilers or outdoor wood heaters/boilers/furnaces) burn wood or other biomass to heat liquid (water or water-antifreeze) that is then piped into occupied buildings to provide heat. Hydronic heaters are typically located outside the buildings they heat, but may also be located indoors. For more information visit: Summary of Requirements for Wood-fired Hydronic Heaters.
There are two major types of wood-burning fireplaces, traditional masonry fireplaces and pre-fabricated "low mass" fireplaces. Most fireplaces, whether masonry or low mass, are not used as a primary source of heat; their function is primarily for ambiance and secondary heating.
Fireplace inserts are similar in function and performance to free-standing wood stoves, but are designed to be installed within the firebox of an existing masonry or metal fireplace. A certified installer will make sure the flue liner in your masonry chimney is installed correctly. If your fireplace is factory built (or "zero-clearance"), you must use an insert that was specifically designed and tested for your unit to make it more efficient and less polluting.
A fireplace retrofit is a device that is installed into an existing wood-burning fireplace. The primary purpose of the retrofit is to reduce wood smoke pollution from existing fireplaces.
Forced-air furnaces (also known as warm-air furnaces) are designed to burn cord wood, wood pellets or wood chips to heat an entire residence. Heat from these furnaces, which are typically located indoors, is distributed through ducts using a blower fan. Stacks or chimneys for these furnaces are generally on the roof of the home they heat. Large forced-air furnaces are capable of outputting 65,000 BTU per hour or more while small forced-air furnaces output less than 65,000 BTU per hour. For more information visit: Summary of Requirements for Wood-fired Forced Air Furnaces.
A masonry heater is a site-built or site-assembled solid-fueled heating device, consisting of a firebox, a large masonry mass, and a maze of heat exchange channels. It stores heat from rapidly-burning fires within its masonry structure, and slowly releases the heat into the home throughout the day. Masonry heaters currently do not require EPA certification.
Alternatives to Wood Burning
In addition to wood-burning appliances there are also alternative heating options, including:
Gas-fired boilers and furnaces are designed to burn either natural gas or propane. They emit very little pollution, require little maintenance, and can be installed almost anywhere in the home. Today's gas-fired boilers and furnaces can be vented through an existing chimney, or direct vented through the wall behind the stove. While some models do not require outside venting, EPA does not support their use due to indoor air quality concerns. For more information visit: Gas-Fired Boilers and Furnaces.
Decorative fireplace logs can be installed in an existing fireplace. While not designed to be a significant source of heat, decorative logs provide an alternative to burning wood. Because they burn either natural gas or propane, they have low pollution emissions.
Installation, Maintenance and Regulatory Requirements
A wood-burning appliance that is sized and placed properly with a venting system that delivers adequate draft will reduce wood consumption, produce more usable heat, and reduce maintenance from inefficient fires. Experienced professionals will properly size and place equipment for the best heat distribution.
A certified technician should install your EPA-certified wood stove or fireplace insert to ensure proper performance. A certified technician should also conduct annual maintenance on the system to ensure it continues to perform as intended.
Whether installing a wood-burning appliance yourself or utilizing a certified professional, a permit and inspection is required by your local Building Department to ensure the installation meets the proper building and fire codes.
Note: Outdoor Wood Burning Furnaces (OWFs) constructed, installed, established, or modified after July 8th, 2005 must comply with the provisions of Connecticut General Statute 22a-174k. Read Connecticut Outdoor Wood-Burning Fact Sheet (PDF) for more information.
To assist small business owners who manufacture and distribute new residential wood stoves, pellet stoves, hydronic heaters and wood-fired forced air furnaces, EPA and DEEP developed the following compliance guides:
Properly installed, correctly used wood-burning appliances should be smoke free. If you see or smell smoke, you may have a problem. An efficient fire requires good firewood, using the right wood in the right amount, and good fire building technique.
Get the best efficiency from your wood stove or fireplace using the following steps:
Wood heaters manufactured before 1990 burn wood less efficiently, which wastes fuel, pollutes outdoor air and creates dust in your home. Replacing an old wood heater or fireplace with a more energy efficient appliance can save fuel, money, and protect you and your family's health. Many cleaner, energy saving options are certified by the EPA. In general, the lower the emissions, the higher the efficiency.
A newer, properly installed wood heater produces a hotter fire, which requires less fuel and releases little smoke. Make sure your wood heater is an EPA-certified appliance. To identify an EPA-certified appliance, look on the back for a metal tag, refer to your owner's manual or check the list of appliances. Heaters with solid doors are generally older and should be replaced and disposed of properly. To learn more, visit how to choose an appliance.
If you burn firewood, make sure it is dry, or seasoned. Wet wood can create excessive smoke. Moisture meters allow you to test the moisture level in wood, and can be bought at hardware stores or on the internet. Properly dried wood should have a reading of 20% or less. Hard wood tends to have the most energy per cord. Use the following steps to prepare wood to burn efficiently:
Split wood into pieces 6 inches in diameter or smaller for faster drying.
Stack off the ground, split side down
Cover stack to protect the wood from rain and snow
Store for at least 6 months for softwood, and at least 12 months for hardwood.
If you burn wood pellets, burn pellets certified by the Pellet Fuels Institute (PFI) and always keep your pellets dry and pellet heater clean and well maintained.
Weatherizing your home by sealing and insulating cracks and crevices can help reduce overall heating needs and heating bills. Caulk around windows, doors, and pipes to seal air gaps and add weather stripping to doors and windows. Check out EPA's ENERGY STAR home improvements page for additional tips.