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Outdoor Wood-Fired Boilers
Outdoor Wood-Fired Boilers
Outdoor wood-fired boilers are not allowed in the state of
Washington at this time. This site is designed to help you
get the facts before purchasing a wood-fired boiler. If you have
any questions about outdoor wood-fired boilers, please contact
us.
With the rising cost of heating oil, more Washington
residents are looking to wood as a source of heat and hot water.
But not all wood heat is the same. While indoor wood stoves have
been tested and certified by EPA for emissions since 1990,
outdoor wood boilers (OWBs) are not. OWBs cause dense smoke and
have very short smoke stacks, so the smoke is released at levels
where people breathe it. This smoke endangers your health and
that of your family and neighbors, as well as harming the
environment. Even the cleanest outdoor wood-fired boilers are 3
to 5 times more polluting than a certified wood stove meeting
Washington emission standards.
What are outdoor wood-fired boilers (OWBs)?
OWBs are wood-fired water heaters that are located outdoors
or are separated from the space being heated. The fires in the
large fire boxes heat water that is circulated into the home
through underground pipes. The energy may be used to heat
houses, shops, domestic hot water, greenhouses, swimming pools
and spas. Indoor installed boilers are a variation of an OWB.
They are in the same legal category as OWBs, and subject to the
same regulations.
Are any OWBs legal in Washington?
Not at this time. However, Ecology is willing to consider
allowing OWBs to be sold in Washington if the manufacturers can
prove they meet Washington's standards. To prove an OWB meets
Washington's standards, a manufacturer must:
- have the device tested using a test method that Ecology considers adequate and acceptable; and
- submit test results to Ecology showing the OWB emits no more than 4.5 grams of fine particles per hour.
The U.S. Environmental Protection Agency has a voluntary
program for manufacturers of outdoor wood-fired boilers.
Boilers that are accepted into this program meet stricter
guidelines and pollute less. However, even these boilers
pollute too much to be allowed in Washington. You can find more
information on this program at
http://www.epa.gov/owhh/models.htm.
What causes OWBs to smoke?
Most OWBs employ very primitive combustion technology. When
the water circulating through the furnace reaches an upper set
point (usually around 180°F) the air supply to the fire is
cut-off, cooling the fire so the water will not overheat. The
furnace operates in this "idle" mode until the water temperature
hits a lower set point and the air supply is re-established.
Under some conditions, the OWB may be in idle mode far longer
than in operating mode. This type of operating causes very poor
combustion and heavy foul smoke. Most of the smoke emitted is
fine condensed organic material that does not burn under cool,
oxygen starved conditions. Burning wood with too much water
content (20% moisture or less is required by state law) can also
cause poor combustion. Wood from the outdoor winter wood pile
may be very cold when loaded into the OWB causing an even colder
fire.
Are OWBs worse than indoor wood stoves?
Yes. Newly manufactured indoor wood stoves are required to
meet strict Washington State particle emissions standards, 2.5
grams per hour for catalytic stoves and 4.5 grams per hour for
noncatalytic stoves. In contrast, tests done by the Northeast
States for Coordinated Air Use Management (NESCAUM) found that
the average fine particle emissions (a particularly harmful
pollutant) from one OWB are equivalent to the emissions from 22
EPA certified wood stoves, 205 oil furnaces, or as many as 8,000
natural gas furnaces. One OWB can emit as much fine particle
matter as four heavy duty diesel trucks on a grams per hour
basis. The smallest OWB has the potential to emit almost one and
one-half tons of particulate matter every year. Although older
style indoor wood stoves emit more than new certified stoves,
they are still several times less polluting than OWBs. Due to
their poor combustion conditions, it is also probable that OWBs
emit proportionately more benzene, polycyclic aromatic
hydrocarbons, formaldehyde and other toxic partial combustion
products which have been linked to asthma, heart attacks and
cancer.
Is Natural Wood Smoke Harmful?
Yes, all wood smoke is harmful. Fine particles from smoke
emissions can be carried deep into the lungs and can be
responsible for significant health problems, including asthma,
lung diseases, heart diseases and death. These particles can
also increase the risks of certain types of cancer. Breathing
smoke is especially harmful for sensitive populations, including
children, the elderly, and people with heart and lung ailments.
It is estimated that fine particle air pollution costs citizens
of Washington State hundreds of millions of dollars each year in
health care costs and lost productivity due to illness.
If I want to burn wood, what should I do?
- First, consider your neighbors. Burning wood in dense residential neighborhoods may never be a good idea.
- Have an energy expert inspect your home.
- You may find that more insulation or other energy saving improvements may be a better investment than an expensive wood heating device.
- If you have an older non-certified wood stove, consider purchasing a cleaner, more efficient natural gas, propane, pellet or EPA certified woodstove.
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