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New Hampshire Department of Environmental Services


Woodstoves and outdoor wood-fired hydronic heaters (OWBs) are examples of residential wood heaters. Smoke from residential wood heaters contains emissions of fine particle matter (smoke), carbon monoxide, and other organic products, such as formaldehyde, benzene, and aromatic hydrocarbons, which form from incomplete combustion. The fine particulates of wood smoke, ten microns or less in diameter (a human hair is approximately 70 microns in diameter), can be inhaled deep into the lungs, collect in tiny air sacs (called alveoli) where oxygen enters the blood, and cause breathing difficulties and sometimes permanent lung damage.

Wood smoke is a particular concern in the winter, when cold stagnant air and temperature inversions limit air movement. 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 wood heater design have resulted in manufacturing of cleaner-burning units. The use of these cleaner-burning units, in conjunction with best management practices, can reduce and minimize any adverse health and environmental impacts associated with using these devices.

Burning Efficiently

You can reduce the amount of smoke from woodstoves and OWBs by choosing low-emission units certified by the Environmental Protection Agency (EPA); see Regulations below. Proper operation improves combustion efficiency, reduces emissions, helps protect public health and the environment, and saves fuel costs. A few recommended best management practices for installation and operation of a wood heater include:

  • Follow manufacturer recommendations for installation and operation of your specific wood heater.
  • Burn only dry, seasoned wood. Avoid burning wet, rotted, diseased, or moldy wood. Do not burn household garbage, pressure treated wood, painted wood, plywood, oil or chemical stained wood, or wood glued or treated in any way. It is against the law!
  • Conduct routine maintenance to keep the wood heater operating at its peak efficiency. EPA and fire officials recommend that your wood heater, chimney, and vents be professionally inspected and cleaned each year to keep them in safe working order.


New Hampshire does not currently regulate indoor wood stoves, but does encourage the use of EPA certified wood stoves. For more information on indoor wood stoves please visit EPA's Burn Wise website at

United States Environmental Protection Agency

On February 3, 2015, the EPA finalized its New Source Performance Standards (NSPS) for emissions from woodstoves and OWBs. These new emission standards reflect the significantly improved technology available to manufacturers to make cleaner burning and more efficient wood heaters. They will provide important health benefits to communities across the country and build on the work that manufacturers, states, and local communities have done to improve air quality.

Outdoor Wood Boilers:

Under EPA's 2015 NSPS, manufacturers can only sell OWBs in the U.S. that meet the emission limits listed below. EPA does not establish installation criteria, which it has left up to individual states to establish.

  • Starting January 1, 2016, all OWBs sold in the US must meet the particulate matter emission limit of 0.32 pounds per million Btu heat output (0.32 lbs/MMBtu). (Please note that since April 1, 2010, NH Law (RSA 125-R) has required all OWBs sold in NH to meet this emission limit.)
  • Starting January 1, 2020, all OWBs sold in the US, including in NH, must meet the particulate matter emission limit of 0.10 lbs/MMBtu heat output.

Wood stoves:

Under EPA's 2015 NSPS, manufacturers can only sell woodstoves in the U.S. that meet the emission limits established by EPA in its NSPS. Since NH does not regulate woodstoves, please visit EPA's Burn Wise website for more details regarding your purchase and operation of an EPA-certified wood stove.

New Hampshire Law

Outdoor Wood Boilers: On August 10, 2008, NH RSA 125-R Outdoor Wood-Fired Hydronic Heaters established requirements on the sale and installation of OWBs. Since April 1, 2010, RSA 125-R has prohibited the sale of any OWB not meeting the emission limit of 0.32 lbs/MMBtu of heat output (also referred to as a Phase 2 unit). In NH, all Phase 2 units must be installed 50 feet or more from the nearest property line. NH RSA 125-R provides detailed installation and operation criteria for OWBs, including older non Phase 2 units.

Wood stoves: New Hampshire does not regulate residential wood stoves, but does encourage the use of EPA-certified wood stoves. For more information, please visit EPA's Burn Wise website.

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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