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Author – Oliver Beauchemin

On Jan 3, 2014, the U.S. Environmental Protection Agency (EPA) proposed updates to its air emissions standards for new residential wood heaters that would strengthen its requirements for new woodstoves, while establishing air standards for new pellet stoves and several other types of new wood heaters for the first time.  The proposal would phase in emission limits over a five-year period, beginning in 2015.  The proposed standards would apply only to new wood heaters and will not affect wood heaters already in use in homes or currently for sale today. 


Woodstoves are usually made of cast iron or steel and burn split logs to provide heat.  EPA’s proposed updates would limit the amount of particle pollution, also known as particulate matter (PM), from two types of newly manufactured woodstoves:  adjustable burn-rate woodstoves; and single burn-rate woodstoves. The proposed limits also are expected to reduce emissions of other pollutants founds in wood smoke. 

o   Adjustable burn-rate woodstoves (covered by EPA’s current requirements) are designed to allow the owner to adjust the air flow to change the rate at which wood burns.  EPA’s proposed rule would update and strengthen its existing emission limits for these stoves in two steps over a five-year period: 

In Step 1, PM emissions limits would be identical to these currently required by the State of Washington for noncatalytic stoves.  Most adjustable-rate, EPA-certified woodstoves manufactured in the U.S. today already meet the Washington state emission standards. 

To ease the transition to cleaner stoves, EPA is proposing to allow manufacturers of adjustable burn-rate wood stoves that are already EPA-certified to continue manufacturing those stoves until the current certification expires, up to a maximum of five years. 

In Step 2, woodstoves would have to meet strengthened emissions limits(see table below). 

  • Single burn-rate wood stoves (not covered by EPA’s current requirements) are designed so the owner does not need to adjust the air flow.  Single burn-rate stoves would have to meet the same emission limits as adjustable burn-rate stoves. 
  • Pellet stoves are similar in external appearance to wood stoves but burn a fuel made of grounds, dried wood and other biomass wastes that are compressed to form pellets.  Owners pour pellets into a hopper, which feeds the pellets automatically into the stove.  Unlike woodstoves, most pellet stoves need electricity to operate. 
  • Most pellet stoves are exempt from EPA’s current New Source Performance Standards (NSPS) for Residential Wood Heaters.  Under the proposed rule, all pellet stove would have to meet same emission limit as for woodstoves, in the same two-step process.

Proposed Emissions Limits for New Woodstoves and pellet stoves


Proposed PM Limit

Compliance Deadline

Step 1: For all stoves without current EPA certification

·  4.5 grams per hour of operation for catalytic and noncatalytic stoves.

60 days after final rule is published in the Federal Register.

Step 2: All woodstoves and pellet stoves

·  1.3 grams per hour for catalytic and noncatalytic stoves

5 years after the effective date of the final rule.

  • EPA is also seeking comment on phasing in proposed emissions limits over eight years.  This approach would include an interim emissions limit of 2.5 grams per hour three years after the final rule is published in the Federal Register.


  • Each model line subject to the proposed rules would be required to demonstrate compliance through performance testing, similar to requirements of the current wood stove regulations.  Under this certification program, one representative appliance is tested by an accredited laboratory to demonstrate compliance for an entire model line.  EPA is proposing this approach rather than requiring manufacturers to test every heater to minimize testing costs to manufacturers, most of which are small businesses.
  • The proposed rule also includes test methods that manufacturers would have to use to determine PM emissions and demonstrate compliance.
  • To strengthen compliance assurance and consumer confidence, the proposed standards would require testing and certification by internationally accredited laboratories and certification bodies.  EPA would also review the tests and make the results available to consumer on a website.

~ Oliver Beauchemin

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