Wood Stoves

Residential wood heaters, which includes wood stoves and outdoor boilers, contribute significantly to particulate air pollution. EPA has regulated wood stove particulate emissions since 1988. Wood stove model lines that are in compliance with the rule are referred to as EPA-certified wood stoves.

Wood Heaters sold in the United are required to undergo emission testing to comply with U.S. Environmental Protection Agency (EPA) New Source Performance Standards (NSPS) guidelines and safety testing to comply with Consumer Products Safety Commission and insurance requirements. The safety testing requirements determine the clearance and installation requirements for a wood heater. This section of the Combustion Portal addresses EPA NSPS (New Source Performance Standards), but does not cover Consumer Products Safety Commission and insurance requirements.

General

At a federal level, air emissions from wood stoves and certain pellet stoves (only units with air to fuel ratio less than 35 to 1) are regulated by EPA through New Source Performance Standards (NSPS), which are rules aimed at manufacturers and retailers of these devices. The NSPS define a wood stove as an enclosed, wood burning appliance capable of and intended for space heating and domestic water heating that meets the following criteria:

• Air to fuel ratio less than 35 to 1;
• Usable firebox volume less than 20 cubic feet;
• Minimum burn rate less than 5 k/hr as as determined by Reference Method 28 test conducted by an EPA accredited laboratory and; and
• Maximum weight less than 800 kg.

The NSPS specify a maximum amount of air pollution that the units can generate. Testing must be performed by the manufacturers at laboratories using approved test methods for each model of stove sold in order to be certified for sale. The NSPS have been in effect for more than 20 years. 

In addition to federal regulations that apply to all wood stove manufacturers, some states have enacted more stringent regulations. Also, many local jurisdictions have ordinances and rules in place that impact installation and use of wood stoves.

New Source Performance Standards (NSPS)

EPA's New Source Performance Standards (NSPS) for residential wood heaters fall under Section 111 of the Clean Air Act. The standards govern the manufacture and sale of new residential wood heating devices and do not apply to existing wood stoves and other wood heaters installed in peoples' homes. The following are major regulatory actions concerning residential wood heaters:

• On February 26, 1988, EPA issued New Source Performance Standards (NSPS) that govern the manufacture and sale of new wood stoves, and certain wood burning fireplace inserts built after 1988. The 1988 standards were amended on November 24, 1998, to prohibit the sale of wood heaters that had their original certification revoked due to an invalid certification test. This action did not affect wood heaters that had already been sold to consumers.

• On February 3, 2015, EPA strengthened its New Source Performance Standards (NSPS) for residential wood heaters to make new heaters significantly cleaner. The updates, which are based on improved wood heater technology, strengthen the emissions standards for new woodstoves, while establishing the first-ever federal air standards for previously unregulated new wood heaters, including outdoor and indoor wood-fired boilers (also known as hydronic heaters), indoor wood-fired forced air furnaces, and single burn-rate woodstoves. The final rule will phase in emission limits over a five-year period, beginning tin 2015. T (See: FACT SHEET: Summary of Requirements for Woodstoves and Pellet Stoves | Controlling Air Pollution from Residential Wood Heaters | US EPA). 

• On April 2, 2020, the United States Environmental Protection Agency (EPA) published the finalized amendments to the 2015 New Source Performance Standards (NSPS) for New Residential Wood Heaters, New Hydronic Heaters and Forced-Air Furnaces (collectively referred to as “wood heating devices”). This rule amends the 2015 NSPS by removing certain minimum requirements for pellet fuels and clarifying a requirement regarding the use of unseasoned wood in pellet fuel production. (see Fact Sheet)

For more NSPS information, see Regulatory Actions for Residential Wood Heaters.

State Initiatives and Laws

With the increasing use of wood stoves nationwide, there is growing concern about the health and environmental effects of wood smoke. The burning of wood is known to produce a complex mixture of particulate and gaseous emissions. It can be a local problem because wood smoke is typically emitted close to the ground and is highly dependent on wind characteristics to dilute or disperse it. In response to these issues, many northern U.S. states and some southern states have implemented strategies to reduce air pollution from wood stoves. These strategies range from publishing good practices to enacting regulations with emissions standards (e.g.,WA) more stringent than the Phase 2 NSPS. Also, some states provide incentives such as rebates on purchases of more efficient stoves. Click on the state initials below to find more information for your state for wood stoves.

Wood Stoves:

To report errors or updates on the above tables, please email George Cushnie.

Local Ordinances

Numerous jurisdictions have established legal requirements to reduce wood smoke. For example, some communities have restrictions on installing wood-burning appliances in new construction (see examples). The most common and least restrictive action is to limit use at those times when air quality is threatened. The appropriate agency issues an alert, similar to the widespread Ozone Action Day alerts. For more information, contact your local city or county government.

More Resources

EPA's Burn Wise website. A partnership program of the U.S. Environmental Protection Agency that emphasizes the importance of burning the right wood, the right way, in the right wood-burning appliance.

Choosing the Right Wood Burning Stove. Today’s wood stove models feature improved safety and efficiency--they produce almost no smoke, minimal ash, and require less firewood. While older uncertified stoves release 15 to 30 grams of smoke per hour, new EPA-certified stoves produce no more than 4.5 grams per hour.