Caution Urged for Outdoor Wood-Fired Boilers

The high cost of petroleum-based fuels for home heating has Iowans looking at alternative sources. In both rural and residential areas, some Iowans have purchased or are considering outdoor wood-fired boilers (OWBs) or furnaces. Department of Natural Resources (DNR) officials caution against burning any wood other than untreated, well-seasoned wood and advise that OWBs can be more polluting and less efficient than other home heating devices.

“Unlike residential wood burning stoves, OWBs are not required to meet federal emission standards,” says Christine Paulson, an air specialist with the DNR Air Quality Bureau. “We’ve received a number of complaints about the OWBs, and our investigations have revealed that many of the concerns raised are valid. Because of the large fireboxes on the units, some people have jumped to the conclusion that anything can be burned in them.”

OWBs are free-standing wood burning devices that heat water, which is then pumped to one or more structures to provide heat. They look like a small shed with a short smokestack on top. They may be used to heat homes and outbuildings, produce domestic hot water, heat hot tubs or provide heat to agricultural operations. OWBs are also called Outdoor Wood-fired Hydronic Heaters (OWHH).

Household garbage and debris contain chemicals that are illegal to burn in such devices without an air permit. Burning such items releases toxic air pollutants, some of which are carcinogens.

“We had a case recently where someone was burning railroad ties in his OWB,” adds Paulson. “Railroad ties are treated with creosote, a probable carcinogen. Just handling railroad ties has been shown to cause skin rash and irritation. Imagine what it can be when vaporized and drawn deep into the lungs.”

Even wood smoke from well seasoned hardwood contains fine particle pollution, carbon monoxide, and other pollutants, so it is important to release it through a stack well above roof lines so that children, people with lung and heart disease, and other sensitive groups are not exposed to it.

Before buying an OWB, the DNR asks you to consider the possible health and environmental impact to your family, neighbors, pets and livestock, and to contact your county health department or city hall to see if OWBs are allowed.

“We encourage consumers to choose the cleanest, most efficient models available, preferably EPA-certified units. Then operate and maintain the unit, whether it is new or one of the older models, according to manufacturers’ instructions,” emphasizes Paulson.

The DNR also recommends that OWB operators place the unit at least 500 feet from an adjoining property line, keep the doors of the unit closed unless loading or stoking the live fire, and install a vertical, unobstructed stack that is at least 5 feet taller than the roof line of nearby structures and residences. Never use propellants to start a fire and do not store them near an OWB. A child in Iowa recently died from burns linked to a propellant stored near an operating OWB.

A DNR OWB Fact Sheet with more information is available at www.iowacleanair.com/news/files/OWB_Fact_Sheet.doc. Information on EPA's OWB program, including information on EPA-certified models, is available at www.epa.gov/woodheaters/.

Questions or complaints regarding specific OWB or other wood heaters should be directed to appropriate DNR field offices. A map and contact information for the six DNR field offices is available at www.iowadnr.com/fo/fomap.html or call (515) 242-5100. Those with questions or concerns within Polk County should call (515) 286-3351; or within Linn County call (319) 892-6000. Permit questions may be directed to the DNR Air Quality Bureau permit hotline at 1-877-247-4692.