Remember That Outdoor Wood-fired Boilers Should Be Purchased And Intalled Conscientiously, Say Colorado Health Officials

Main Category: Public Health
Article Date: 10 Oct 2008 - 5:00 PDT

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The Colorado Department of Public Health and Environment once again is reminding the public that outdoor wood-fired boilers, which are gaining popularity as an alternative residential energy source, are subject to state air quality regulations and should be purchased and installed conscientiously.

"These devices are subject to opacity regulations, which govern the thickness of smoke that is generated," said Kirsten King, who manages the Stationary Sources Program for the department's Air Pollution Control Division. "It is important that consumers do their homework before purchasing one of these devices. Be certain that the manufacturer is reputable, that the device is installed properly, and that it is properly and regularly maintained."

Outdoor wood-fired boilers are wood-fired water heaters that are located outdoors and are separated from the home or building being heated. At first glance, they look like outdoor sheds with smokestacks.

Fires in the boilers' 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.

Since last year, Colorado retailers have seen a surge in the purchase and installation of outdoor wood-fired boilers as an alternative to more traditional natural gas-fired furnaces and other devices as home heating sources.

One reason for the growing popularity of the boilers is the availability of inexpensive and/or free wood to stoke them - a result of the mountain pine beetle infestation in North-Central Colorado and from other forest restoration and wildfire mitigation activities occurring throughout the state.

However, the devices can be a significant source of air pollutant emissions.

"We receive complaints every year about these devices," King said. "They can really generate a lot of smoke and impact an entire neighborhood. Air quality in the immediate area can be significantly reduced."

King emphasized that consumers have options when considering an outdoor wood-fired boiler. While there are a number of boiler manufacturers, only a handful utilize cleaner-burning technology. Most of the boilers employ primitive combustion technology. When the water circulating through the furnace reaches a certain temperature, 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 temperature and the air supply is re-established. This results in poor combustion and potentially heavy smoke.

Most of the smoke emitted is fine condensed organic material that does not burn under cool, oxygen-starved conditions. The choice of wood also can have an impact how much smoke the boilers generate.

For example, green wood full of moisture causes poor combustion. Wood from an outdoor winter woodpile also may be very cold when loaded into a boiler, causing less efficient fires. Wood from urban sources (demolition and/or construction debris) should not be used as it may include paints, glues or other contaminants that exacerbate the pollution potential.

Outdoor wood-fired boilers are subject to provisions of Colorado Air Quality Control Commission Regulation No. 1, which details emissions controls for particulate matter, smoke, carbon monoxide and sulfur oxides. Regulation No. 1 sets a 20 percent opacity standard for such devices.

If found to be in violation of the opacity standard, the owner or operator of the device may be subject to an enforcement action from the Air Pollution Control Division that could result in a fine.

The Colorado Department of Public Health and Environment urges residents to educate themselves regarding outdoor wood-fired boilers. Information is available on-line through sites like http://www.woodheat.org and a variety of state-run sites.

Colorado Department of Public Health and Environment