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New Hampshire Department of Environmental Services

Ideas for a Cleaner Environment
Published monthly by the NH Department of Environmental Services Watershed Assistance Program, Concord, NH (603) 271-7889

October, 2008

Why are Outdoor Wood Boilers a hot topic?

The New Hampshire Department of Environmental Services wants to make people aware of a new law that applies to outdoor wood boilers (also known as outdoor wood-fired hydronic heaters). If you already own an outdoor wood boiler or are thinking about purchasing one, you should know about HB 1405 (Chapter 362, Laws of N.H. 2008), which became effective on August 10, 2008. The new law establishes requirements for the sale, installation and use of these devices.

Outdoor wood-fired boilers (OWBs) are free-standing wood-burning devices that heat water, which is then pumped to one or more structures to provide heat. They resemble a small shed with a smokestack on top. OWBs may be used to heat homes and buildings, produce domestic hot water, heat swimming pools or hot tubs, and provide heat to agricultural operations such as greenhouses and dairies.

Many OWBs are used in rural, cold climates like New Hampshire's, where wood is readily available. Wood is a renewable resource and a valuable fuel source because it is "global warming neutral" when harvested in a sustainable manner. With fluctuating fossil-fuel prices, OWBs can offer a viable alternative heat source, if the cleanest OWBs are purchased and they are installed and operated properly.

A concern associated with certain OWBs is the air pollution they may produce. Smoldering fires and short smokestacks may create heavy smoke close to the ground that sometimes causes a neighborhood nuisance or an adverse impact on public health and the environment.

Fortunately, recent advances in OWB technology have resulted in cleaner-burning units. The new law ensures that these cleaner-burning units are sold in New Hampshire and that they are located and operated in a manner that reduces and minimizes any adverse health and environmental impacts associated with using them. Highlights of the new law include:

  • Sales requirements: Effective January 1, 2009, all OWBs sold in NewHampshire must be certified by EPAas meeting emission limits to reduce particle pollution. After April 1,2010, all OWBs that are sold in the state must be certified by EPA as meetingeven more stringent EPA emission limits.
  • Sellingand Buying responsibilities: Any seller of an OWB is required toprovide written notice to a perspective buyer on New Hampshire's law. Thewritten notice must be signed and dated by the buyer and seller, includespecific information on the OWB purchased, and be kept on file by theseller for at least three years.
  • Setbackand stack height requirements for installation of OWBs: OWBs installedafter August 10, 2008, must meet certain setback and stack heightrequirements, depending on whether they are certified by EPA. For example,OWBs that are not certified by EPA to meet emission limits must be located200 feet from nearest abutting residence. They must also have a stackheight that is two feet higher than the peak of a residence or business notserved by the unit, if that business or residence is located within 300feet of the unit. Setback and stack height requirements for units that arecertified by EPA are less stringent.
  • Permitted fuels: Clean wood and/or wood pellets made from clean wood are the only fuels that can be burned in these devices.
  • Prohibited fuels: Burning other materials such as household trash, tires or construction debris is strictly prohibited.

If you plan to purchase an OWB, NHDES urges you to look for the cleanest model available that is labeled with an EPA hang tag. Consider all alternatives and choose a heating system that is the most efficient and has the least adverse impacts to your family and neighbors. A complete list of EPA certified makes and models can be found at the EPA website

If you already own an OWB, you should install, operate, and maintain it according to state law and the manufacturer's instructions. Any owner that operates an OWB in a manner that is deemed a nuisance or injurious to public health by a municipality or the NH Department of Health and Human Services will be required to abate the nuisance.

For more information on the sale, installation, and use of OWBs in New Hampshire, contact the NHDES Air Resources Division at (603) 271-1370.

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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