Emissions: Particulates and Toxins Indoors and Out
1. If you look at a fire in a fireplace, only part of a log is burning at any given time. The other end is smoldering (incomplete combustion), giving off volatile organic chemicals, including formaldehyde and benzene, carbon monoxide, and particulates often called soot. A log fire gives off 50 grams of particulate matter per hour, compared to 26 g/h for dirty woodstoves, and 4 g/h for high efficiency wood stoves. The EPA standard for woodstoves is 6.5g/h or less as measured at the top of the chimney. Incomplete combustion is highest when starting a fire and as the fire is winding down.
2. Soot particulate is responsible for darkening Arctic and Greenlandic snow and ice, causing it to melt faster and raising sea level.
3. A fast burning fire pulls air from the house to use in combustion, drafting it out the chimney. Indoor air may be pulled from vents for your furnace or water heater, pulling the carbon monoxide fumes from those appliances into the rest of the house. This also disrupts the combustion in those furnaces.
4. At the end of a fire, when the drafting up the chimney is low and carbon monoxide production of the fire is high, CO from the fire may be drawn into the house.Low Efficiency: Fireplaces operate at minus 10% to 10% efficiency
5. Fires take 140% of the heated air in the house up the chimney in an hour (1.4 air changes per hour (ACH) )
6. The air moves so fast up the chimney, heat doesn’t have much time to flow to the room or surrounding masonry. If the chimney is on an exterior wall, masonry heat is transferred to the outside.
7. When not in use, closed dampers continue to let cold air in from outside and warm air out from inside.
8. Glass doors for fireplaces are made of tempered glass so it won’t break from the heat; however, this also means that much of heat from the fire (infrared radiation) does not get out into the room. Fireplace doors can reduce the amount of heated house air drawn up the chimney overnight, at the end of the burning cycle. Solutions
1. Use manufactured logs instead of wood in fireplaces:
Logs made of wax and sawdust burn more completely, last longer ( one lasts 3-4 hours), and draw much less air (and indoor heat) up the chimney. An EPA study found that particulates were reduced by 69% and carbon monoxide emissions lessened by 88% from fires with oak logs. Very little heat is generated.
2. Stop using your fireplace
and plug the chimney to keep the cold air out. Commercial chimney plugs and balloons are available from hardware stores or online. 3. Burn seasoned, dry firewood. Cover your wood to keep it from absorbing rain water.
Stack your wood so it can 'breathe' and let moisture evaporate out. Water in the wood doesn't burn! Aim for a moisture content of 20% or below.4. Install an airtight, high efficiency (70-78%) woodstove
with two combustion chambers for complete combustion and a pyro-ceramic glass door for good heat transfer to the room. It should be placed in a large room that is frequently used. Air change per hour is only about .04. Consult a professional installer to properly size the stove and chimney diameter for best drafting and efficiency.These stoves require operator input to do their best: don't forget to engage the bypass damper and use dry wood. The longer the heat stays in the firebox, the better. High efficiency stoves may qualify for federal and state tax credits!For more detailed information, refer to:
Hearth.com reprinted a Home Energy article by A. C. S. Hayden titled “Energy-efficient, environmentally-friendly, and safe alternatives to the outmoded conventional fireplace are here, and they're aesthetically pleasing too. ...”
C. S. (Skip) Hayden is head of Energy Conservation Technology at the Combustion and Carbonization Research Laboratory (CCRL) of CANMET in Ottowa, Canada.
Technical information on fireplace and woodstove emissions is available from epa.gov