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The EPA's role regulating wood stove emissions

Updated May 2022

The Environmental Protection Agency (EPA) is the federal agency responsible for overseeing the emission standards and certification program for wood and pellet heaters. It began on this journey in the mid-1980s, initially culminating in regulations called New Source Performance Standards (NSPS) on February 26, 1988. By law, the EPA has to review that NSPS every eight years, but it did not begin the process until around 2001.

On March 11, 2020 the EPA finally finished the second NSPS on wood heaters, ruling that the regulations put into place in 2015 would stand, with only very minor changes. Industry had sued the EPA over the 2015 regulations and then the EPA proposed a rulemaking to change some of the compliance dates, to allow for a retailer "sell-through." However, in its March 2020 ruling, it found industry did not present any data to show "manufacturers could not develop Step 2 models in time" and "provided insufficient data showing a percentage decrease in sales approaching 2020."


In 1988, the EPA originally set a particulate emission limit of 7.5 grams per hour for non-catalytic wood stoves and 4.1 grams per hour for catalytic wood stoves. In 1995, Washington State set a 4.5 gram an hour standard, which influenced the entire industry and by the late 1990s, most stoves emitted less than 4.5 grams. In 2015, the EPA adopted the 4.5 limit and as of 2020, the EPA set a standard of 2 grams an hour for wood and pellet stoves, or 2.5 grams an hour if stoves test with cordwood. Click here for key provisions of the new rules.

The EPA program, now three decades old, has helped create a new breed of cleaner residential stoves, helping this important renewable energy technology compete in the modern world. In the late 1980s, hundreds of wood stove makers went out of business because they could not afford to adopt the technologies that would produce cleaner stoves. A few companies will also go out of business as stricter 2020 standards take effect, but unlike in 1988, an overwhelming majority of companies will be able to remain in business and many of them may thrive under these new regulations.

The 1988 regulations have been successful in reducing wood smoke in valleys, towns and cities across America but decades later a majority of stoves in homes still predate EPA emissions regulations and are uncertified. Other than slow turnover of America’s stock of installed stoves, one of the main reasons the 1988 regulations fell short of expectation is because whole classes of new wood heaters cropped up that either fell outside of the regulations or were even specifically designed to avoid EPA regulations. Outdoor wood boilers (OWB, also called hydronic heaters) are the most notorious example.

which has mounted an all-out defense of their members’ right to continue to produce and sell even the smokiest boilers. Advocates for regulation, they charge, are simply trying to stop people from heating with wood. The largest of the U.S. manufacturers is Central Boiler … declined to disclose the emission figures for the company's Classic boilers, one of the most popular units on the market, but he denied flatly that they were a problem."

State began petitioning the EPA to regulate outdoor boilers in the late 1990s and Vermont was the first state to require property setbacks and stack heights in 1997. By 2005, more states were calling on the EPA to take action, during the middle of President Bush’s two terms and the EPA declined, saying even if they were to set a standard it would take 5 to 7 years. By the time the EPA acted, more than a quarter million units of this this pernicious, polluting technology had been sold and installed, almost all in the Great Lake and upper Midwest states and Northeastern states.

The technology led to a deep divide in the wood heating community, with many wood stove advocates proclaiming that outdoor boilers were giving the whole community a black eye. In 2008, one writer summed up the industry side like this: "Dozens of [OWB] manufacturers … are represented by a national trade association, the Hearth, Patio and Barbeque Association,


The EPA launched a voluntary emission program in 2007 to encourage outdoor boiler manufacturers to reduce particulate levels instead of pursuing a mandatory standard and after many delays, it wasn't until the 2015 NSPS that all wood boilers and furnaces were required to meeting emission standards. The 1988 wood heater regulations also left a loophole for wood stoves and a huge trade in uncertified wood stoves blossomed in the United States. Again, the wood heating community was very divided. The Alliance for Green Heat, founded in 2009 began highlighting the problem in 2012 and in 2014 the EPA disclosed that 40,000 of these uncertified wood stoves were being sold each year, which could be up to a third of all wood stove sales. With both exempt wood stoves and outdoor boilers, deceptive and misleading advertising bolstered sales, and the EPA has does not address this.

The EPA staff that regulates wood stoves is based in the EPA’s North Carolina Office of Air Quality Planning and Standards. One of their main functions is to run a major educational campaign called "Burn Wise", a matrix of voluntary efforts. The website has excellent materials and resources for consumers, cities, states and tribes.


Currently, the EPA is focused on developing a cordwood test protocol and is working to replace the federal test method based with an Integrated Duty Cycle (IDC). They also revoked the ASTM cord wood test method, the most popular one with manufacturers, reverting the previous federal test method.

The EPA's Office of Compliance and Enforcement in Washington DC handles enforcement of EPA's wood heater regulations and is in charge of maintaining the database of certified wood heaters, which is a vital new tool for the wood heating community that is still evolving.

The EPA’s Office of the Attorney General has become more active, investigating the EPA’s Office of Enforcement and conducting enforcement on case involving US Stove Co and Tractor Supply.ufacturers, reverting the previous federal test method.

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