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FACT SHEET: Final Updates to Air Emissions Requirements for New Residential Wood Heaters: Changes Since Proposal



On February 3, 2015, the U.S. Environmental Protection Agency (EPA) updated its clean air standards for residential wood heaters to make new heaters significantly cleaner and improve air quality in communities where people burn wood for heat. 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, known as New Source Performance Standards (NSPS), will phase in emission limits over a five-year period, beginning this year. The standards apply only to new wood heaters and will not affect wood heaters already in use in homes.


  • EPA received nearly 8,000 comments on the proposed rule and held a public hearing. Based on those comments and additional information it received, the agency has made a number of changes to the rule, including changes to reflect available emissions test data and changes that will provide manufacturers and retailers time to transition to cleaner heaters. Many wood heater manufacturers are small businesses.
  • The final rule will not apply to masonry heaters, the majority of which are custom-built on site. EPA had proposed to set emissions limits for these heaters, but is not taking final action at this time to allow additional time for the development of emissions testing methods used to determine compliance. EPA will consider whether to finalize requirements for new masonry heaters in the future.
  • To allow manufacturers time to transition their model lines to cleaner wood heating technology, and have emissions tested (a step required for certification), EPA is making the following changes in the final rule:
    • To give manufacturers of wood-burning forced air furnaces the time they need to develop cleaner models and have emissions tested, EPA is requiring work practice standards beginning on the effective date of the rule, and phasing in emissions limits in two steps based on furnace size between 2016 and 2020. Small furnaces will have to meet the Step 1 emissions limit by 2016; large furnaces will have to meet it by 2017. All furnaces must meet the Step 2 emissions limit by 2020.
    • EPA changed the Step 1 emissions cap (part of testing requirements) for hydronic heaters in the final rule to match the current requirements of the agency’s voluntary Hydronic Heaters Program. This change will allow most models that are “Phase 2 qualified” under the voluntary program to be automatically certified as meeting the first emissions limit in the final rule, further reducing the potential for testing delays. This certification will be good until 2020, when the Step 2 emissions limit takes effect.
    • To reduce potential certification delays, EPA will allow a conditional certification for up to one year for woodstoves, pellet stoves and forced air furnaces if a manufacturer submits a complete certification application that includes a full emissions test report by an EPA-accredited laboratory and meets other application requirements.
      • To ease the transition to cleaner stoves, EPA’s final rule will allow retailers to sell woodstoves that meet requirements of EPA’s 1988 rule and for hydronic heaters until December 31, 2015. After that date, any new woodstoves and hydronic heaters sold at retail in the U.S. must meet the Step 1 emissions limit.
  • Based on public comment on the proposed rule and additional review, EPA has determined that the agency does not yet have sufficient data to require that emissions from woodstoves and hydronic heaters be tested using fires that burn cordwood (split wood). Instead, manufacturers will be required to test emissions using “cribs” – the same type of testing used for the 1988 wood stove standards. A crib consists of lumber assembled in a standardized configuration that is based on the type of heater being tested.
  • EPA believes development of wood heaters that perform well in cordwood testing is important, because cordwood is what consumers use. The agency will allow cordwood testing for woodstoves and hydronic heaters with prior approval. In addition, to encourage further development of cordwood test methods, EPA is including an alternative, slightly higher, Step 2 emissions limit based on cordwood testing for woodstoves and hydronic heaters. Based on data available to EPA at this time, the agency anticipates this alternative limit would be at least as stringent as the emission limit for crib testing.
  • Manufacturers may test using either cribs or cordwood in Step 2, and must meet the limit corresponding to the type of test they choose. (Manufacturers testing with cordwood for Step 1 must meet the same emissions limit as those testing using cribs.)
  • Manufacturers choosing to test woodstoves or hydronic heaters with cordwood will be required to have EPA approval of the test method before they can use the alternative limit for Step 2. Any manufacturer that tests wood heaters using cordwood will be allowed to use a special EPA label that will recognize that emissions from cordwood testing more closely reflect emissions from in-home use. Use of this label is voluntary.

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