With several lawsuits on the horizon if it did not act, the EPA has proposed to revise its Clean Air Act (CAA) New Source Performance Standards (NSPS) governing emissions from a variety of wood-burning appliances that provide residential heat.  As with the existing 1988 NSPS for wood-heating adjustable-burn-rate woodstoves, the proposed revisions would phase in limits for particulate matter (PM). 

The proposal would also expand the covered appliances to include pellet stoves not addressed in the 1988 NSPS, wood-fired hydronic heaters, forced-air furnaces, masonry wood heaters, and single burn-rate stoves. Wood-burning appliances not covered by the proposal include outdoor fireplaces, pizza ovens, and barbecues as well as heaters that are fueled solely by oil, gas, or coal. 

The proposed NSPS would apply mainly to manufacturers in a sector dominated by small businesses.  Companies would need to have representative models certified by an accredited third-party laboratory.  The proposal would also make it a federal offense to operate a certified wood-heating appliance in a way that is not consistent with the owner’s manual.

Advanced technologies

Nationally, residential wood combustion accounts for 44 percent of total stationary and mobile polycyclic organic matter emissions, nearly 25 percent of all area source air toxics cancer risks, and 15 percent of noncancer respiratory effects.  Residential wood smoke causes many counties in the United States to either exceed EPA’s health-based national ambient air quality standards for fine particles or places them on the cusp of exceeding those standards. 

Environmental groups, the attorneys general of seven states, and the Puget Sound Clean Air Agency threatened the EPA with court actions if the Agency did not move to revise the 1988 NSPS for wood heaters.  The CAA directs that the EPA revise NSPSs every 8 years to ensure that new sources of air pollution are held to pollution limits achievable with the best system of emissions reduction.

The EPA readily concedes that wood-heater technology has “greatly improved” since the last revision of the NSPS and adds that the proposed standards recognize the cleaner, more efficient technologies developed in recent years.  For most of the appliances covered, the proposal would result in an estimated 80 percent reduction in fine particle pollution over estimated emissions without the revisions.

Proposed limits

The EPA is proposing to phase in emissions limits over 5 years for most wood heaters to allow manufacturers time to adapt emissions control technologies to their particular model lines.   For new wood stoves, pellet stoves, hydronic heaters, and forced-air furnaces, the emissions limits would be phasedin in a two-step process.   The form of the NSPS differs for new masonry heaters.

Wood stoves and pellet stoves

• Step 1: For stoves without current EPA certification, the proposed limit is 4.5 grams per hour of operation for catalytic and noncatalytic stoves, with a compliance deadline 60 days after final rule is published in the FR.
• Step 2:  For woodstoves and pellet stoves, the proposed PM limit is 1.3 grams per hour for catalytic and noncatalytic stoves, with a compliance deadline 5 years after the effective date of the final rule.

Hydronic heaters

• Step 1:  The proposed PM limit is 0.32 pounds per million Btu heat output, with a cap of 7.5 grams per hour for individual test runs, with a compliance deadline 60 days after the final rule is published in the FR.
• Step 2:  The proposed PM limit is 0.06 pounds per million Btu heat output, with a compliance deadline 5 years after the effective date of the final rule.

Masonry heaters

Manufacturers would have to meet the emissions limit by one of two deadlines, depending on the number of heaters they build in a year.

• For 15 heaters or more, the proposed PM limit is 0.32 pounds per million Btu heat output, with a compliance deadline 60 days after the final rule is published in the FR.
• For fewer than 15 heaters, the proposed PM emissions limit is 0.32 pounds per million Btu heat output, with a compliance date 5 years after the effective date of the final rule. 

Industry support

According to the EPA, the proposed standards have been developed with the involvement of industry stakeholders.  For example, the EPA notes that the Hearth, Patio and Barbecue Association has written to the Agency in support of a federal regulation for outdoor wood-fired hydronic heaters. 

EPA’s proposed NSPS for residential wood heaters and related information