January 14, 2011 

Gina McCarthy 

Assistant Administrator for Air & Radiation 

U.S. Environmental Protection Agency 

Ariel Rios Building 

1200 Pennsylvania Avenue, N.W. 

Mail Code: 6101A 

Washington, DC 20460 

Dear Assistant Administrator McCarthy: 

The Northeast States for Coordinated Air Use Management (NESCAUM) urges you to expeditiously 

move forward with health protective revisions to the New Source Performance Standards (NSPS) for 

residential wood heaters. Wood combustion is an important contributor to overall fine particulate matter 

(PM2.5) inventories and represents one of the largest direct sources of PM2.5 in many areas of the country. 

The science has clearly established causal associations between PM2.5 exposures from wood smoke and 

adverse health outcomes, including aggravation of respiratory conditions such as asthma, cardiac 

conditions such as heart disease, and premature mortality. 

With the trend toward increased use of renewable fuels such as wood, we must ensure that new residential 

wood heating units are as clean burning and efficient as possible. It has been more than 20 years since 

EPA has reviewed this standard and since that time, internationally, significant improvements have been 

made in wood combustion technology. Unfortunately, the lack of a domestic regulatory driver to keep 

pace with technological improvements has limited the introduction of cleaner and more efficient units in 

the United States. Moreover, there are fundamental issues with the current outdated NSPS, including the 

broad spectrum of unregulated devices that are currently in or about to enter the market, that EPA must 

address as it revises the residential wood heater NSPS. Many of these issues were detailed in 

NESCAUM’s August 20, 2010 letter to Mr. Gilbert Wood at EPA’s Office of Air Quality Planning and 

Standards (see accompanying enclosure). 

Recent ambient air quality data obtained from continuous PM monitors show increased localized PM 

levels from wood smoke that are higher than previously known. This information, combined with the 

disproportionate impact attributable to residential wood heaters, leads NESCAUM to urge EPA to adopt 

particulate matter emission standards at levels that are significantly lower than those found in the current 

NSPS and voluntary wood heater programs. This will ensure public health protection given that these are 

units located in a variety of urban, suburban, and rural residential settings. We also encourage EPA to 

propose carbon monoxide standards to ensure that these units burn cleanly and efficiently. 

It is also imperative that EPA expand a revised NSPS regulation to apply to all residential wood heating 

devices, such as outdoor hydronic heaters (also known as outdoor wood boilers), indoor wood and pellet

furnaces, outdoor wood and pellet furnaces, pellet stoves, and fireplaces. History has shown that if left 

unregulated, the industry will design devices to avoid regulation such as has been the case with the air to 

fuel ratios and exempt devices in the current standard. 
2

Finally, we urge EPA to adopt tools that would enable states to address units that do not operate at 

certification levels in the field, such as a visible smoke requirement limit based on EPA Test Method 22. 

The current NSPS requires only “model” certification in a lab test. This leaves enforcement programs 

with no tools to address units that are operating improperly in the field. A visible smoke limit will ensure 

that units are designed and operated properly. The current regulation only requires that units be designed 

to burn cleanly but leaves the door open for large variations in emission levels in the field due to lack of 

proper operation, including the mis-use of fuels. 

We strongly applaud EPA’s efforts to work with states on this critical sector and we look forward to 

proceeding with you to achieve robust and effective performance standards for this source category. We 

hope that you will make this critical issue a priority for the agency, and ensure that a timely and health 

protective NSPS is promulgated for the full suite of residential wood heating devices. 

Respectfully, 

Arthur Marin, Executive Director 

NESCAUM 

Enclosure: Aug. 20, 2010 letter to Mr. Gilbert Wood, EPA 

cc: NESCAUM Board of Directors 

 Dan Johnson, WESTAR 

 Greg Green, OAQPS 

 Chebryll Edwards, EPA OAQPS 

 Gil Wood, EPA OAQPS 

 Dave Conroy, US EPA Region 1 

 Bill Baker, US EPA Region 2 
August 20, 2010 

Mr. Gilbert Wood 

USEPA/Office of Air Quality Planning & Standards 

109 T.W. Alexander Drive, Mail Code: C404-05 

Research Triangle Park, NC 27709 

RE: Revisions to Residential Wood Heater NSPS 

Dear Mr. Wood: 

The member states of NESCAUM strongly support a revision to U.S. Environmental Protection 

Agency’s (EPA’s) Residential Wood Heater New Source Performance Standard (NSPS). Wood 

combustion is an important contributor to fine particulate matter in the Northeast, and science has 

clearly established causal associations between fine particles and the aggravation of respiratory 

conditions such as asthma, cardiac conditions such as heart disease, and premature mortality. Recent 

emissions inventories indicate residential wood combustion represents 25 percent of primary fine 

particulate emissions in the Northeast. 

Significant improvements have been made worldwide in wood combustion technology since EPA’s 

current NSPS requirements were phased-in more than 20 years ago. The lack of a modern regulatory 

driver to keep pace with the technology improvements has limited their introduction in the United 

States. 

There are significant additional issues with the existing out-dated standards, including the broad 

spectrum of unregulated device types currently in or about to enter the market. Key issues that the 

NESCAUM states would like addressed in a revision to the NSPS are detailed in this letter, and 

include: (1) the types of units regulated under the NSPS; (2) pollutants covered under the standard; 

(3) fuel types; (4) test methods; (5) third party methods; (6) compliance assurance; (7) level of the 

NSPS; (8) the form of the NSPS; and (9) current inventory of existing residential wood burning 

devices. 

We offer the following suggestions as a constructive contribution to a shared concern between EPA 

and the NESCAUM states. Ultimately, we believe that improving wood heater technologies to 

reduce emissions of pollutants and improve energy efficiency will be good for human health, good 

for the environment, and good for promoting increased use of wood fuel and decreased use of nonrenewable and imported sources of energy. 

1. Units Regulated under the NSPS

The universe of devices regulated under the NSPS is of critical concern to the NESCAUM states. 

Currently, the regulation exempts broad categories of devices, including fireplaces, masonry heaters, 

pellet stoves, outdoor/indoor wood boilers, and outdoor/indoor wood furnaces. NESCAUM urges 

EPA to ensure that the NSPS rulemaking includes emission standards for all residential wood 

burning devices. In addition, NESCAUM supports efforts to eliminate source category loopholes, 
2

thus ensuring that all residential wood heating devices are required to meet an emission standard. 

Furthermore, NESCAUM strongly supports a rule that creates mechanisms to push innovation across 

devices types (i.e., technology transfer). 

To this end, NESCAUM requests that EPA consider the following strategies: 

• Move away from regulations based on definitions of device type; 

• Develop emission standards based on heat delivered and feeding mechanism, such as those 

used in the European regulatory model (a suggested format is provided below in Table 1); 

• Develop standards that incorporate all solid fuel devices across source categories, without 

exemptions based on size.1

Table 1. Proposed Regulatory Construct 

Delivered Heat (Btu output) Automatic feed Hand feed 

<8,000 Btu x lb/mmBtu heat output 

No run to exceed y g/hr 

 x lb/mmBtu heat output 

No run to exceed y g/hr 

8,000-35,000 Btu x lb/mmBtu heat output 

No run to exceed y g/hr 

 x lb/mmBtu heat output 

No run to exceed y g/hr 

35,001-120,000 Btu x lb/mmBtu heat output 

No run to exceed y g/hr 

x lb/mmBtu heat output 

No run to exceed y g/hr 

120,001 – 200,000 Btu x lb/mmBtu heat output 

No run to exceed y g/hr 

 x lb/mmBtu heat output 

No run to exceed y g/hr 

>200,000 Btu x lb/mmBtu heat output 

No run to exceed y g/hr 

x lb/mmBtu heat output 

No run to exceed y g/hr 

Recommendations 

• Regulate based on operating parameters rather than device definitions; 

• Eliminate variation in emission standards for catalytic and non-catalytic units 

• Develop emission standards for the entire source category; 

• Expand the NSPS for industrial, commercial, and institutional (ICI) boilers to cover all 

boilers, regardless of size. 

2. Pollutants Covered Under the Standard

Wood combustion emits a variety of pollutants of concern, many of which have been shown to 

produce acute and chronic biological effects. The abundance of fine particulates in wood smoke 

presents perhaps the most serious health risk. Wood smoke, however, also contains numerous other 

chemicals, including carbon monoxide (CO), nitrogen and sulfur oxides (NOx and SOx), volatile 

organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), chlorinated dioxins, and 

mercury. In Europe, emission standards for wood combustion devices go beyond PM, requiring units 

to meet emission limits for CO, NOx, PM, VOCs, and combustion efficiency. Combining a multipollutant approach with a thermal combustion efficiency standard creates significant co-benefits, 

 

1

 For devices that nominally deliver no heat, such as fireplaces or other aesthetic devices, an appropriate alternative 

to establishing an NSPS based on heat delivered would be to establish a mass-based output limit, such as grams per 

hour. An input-based standard (e.g., fuel energy consumed over time) for these types of devices would be 

inappropriate. 
3

including reduced emissions, ensuring no trade-offs among pollutants (e.g., decreasing CO emissions 

to very low levels while increasing NOx emissions), and reduced fuel consumption. Therefore, 

NESCAUM recommends that EPA develop emission standards for residential wood heaters beyond 

particulate matter to include, at a minimum key, the pollutants CO, VOCs, and PAHs. 

Given the federal government’s recent actions to reduce pollutants that impact climate change, 

NESCAUM also strongly recommends the EPA develop emission limits in this NSPS for both CO2-

equivalent (CO2e) and black carbon. Black carbon can have a significant atmospheric warming 

effect. It has been estimated that applying existing technologies could reduce black carbon by 50 

percent, enough to offset the warming effects of one to two decades of CO2 emissions.2

 About 90 

percent of black carbon emissions come from the consumption of fossil fuels and the burning of 

wood and other biomass. Therefore, the NESCAUM states strongly urge EPA to create CO2e and 

black carbon emission standards in this revision of the NSPS. 

 

Recommendations

• Establish standards as mass emissions per unit time for other criteria and air toxic pollutants 

to include CO, VOCs, and PAHs. 

• Establish emission limits for CO2e and black carbon. 

3. Fuel Types and Various Devices 

Today, there are a wide variety of devices that use solid fuels other than wood, such as coal, corn, 

and switchgrass. In order to ensure public health and environmental protection, EPA must require 

that all solid fuels used for residential heating meet an emission standard. Doing so would provide a

level playing field among the various devices and fuels. It is also critical that EPA develop 

regulations covering all devices regardless of type of fuel. 

NESCAUM requests that EPA consider the following: 

• Ensure that dual fuel units are fully tested for emissions from all possible fuels. 

• Expand the regulatory list to include all solid fuels, including coal. 

• Develop fuel specifications for manufactured fuels, e.g., wood pellets. 

Recommendations 

• Expand the residential wood heater NSPS to include all solid fuels (including biomass, wood 

pellets, coal). 

• Develop policies and guidance for testing dual fuel units. 

• Develop fuel specifications for biomass fuels. 

4. Test Methods

Critical to ensuring clean burning units is the use of appropriate test methods that challenge a unit to 

perform at its best under a variety of conditions. While the current program uses a certification 

method in lieu of on-site stack testing to assure compliance, any test performed by the facility for 

 

2

 Wallack, J.S. and V Ramanathan. The Other Climate Changers: Why Black Carbon and Ozone Also Matter, 

Foreign Affairs, 88(5): 105-113 (2009). 
4

certification purposes must conform with the conditions required under other NSPS rules. EPA’s 

own stack testing guidance states the following: 

Facilities are responsible for ensuring compliance with the emission limits under all 

conditions. Therefore, any stack test that is conducted must demonstrate that a facility is 

capable of complying with the applicable standards at all times. As a result, a facility should 

test under the most severe conditions that create the highest emissions. For example, if 

operating at maximum capacity would result in the highest levels of emissions, the facility 

should conduct a stack test operating at maximum capacity or allowable/permitted capacity. 

In addition, the facility should use the highest emitting fuel for the pollutant tested or as 

otherwise justified, and should process material that causes the highest emissions. 

Therefore, test methods used for compliance under this NSPS should meet the following criteria: 

• Emission limits should be based on worst case, rather than average, emissions. 

• The test should simulate worst case conditions that the unit could be operated in the field 

without destroying the unit. This includes burn rates and fuel types. 

• The fuel used should represent the most polluting fuel a homeowner could potentially use. 

Recommendations 

• The test must represent worst case emission scenarios, including burn rate and fuel type. 

• The test should simulate all operations that are feasible in the real world. 

• The test should continue to measure total particulate matter. 

• The test method should be standardized as much as possible across device types, using the 

same fuel, fuel configurations, and burn categories. 

5. Use of Third Party Test Methods 

The NESCAUM states recognize that EPA is under Executive Order to review and adopt, when 

appropriate, third party test methods. The NESCAUM states, however, have significant concerns 

with the wholesale adoption of these methods for several reasons. First and foremost, many state 

agencies have limited ability to participate in processes developing these methods, due to either 

resource constraints or intellectual property policies of third party groups. Second, it is prudent 

public policy that any regulatory test method be scrutinized and issued by the regulator, rather than 

allow the regulated community to develop the test method unchecked. 

Recommendation 

• EPA should scrutinize any third party methods, review the findings, and discuss with states, 

locals, and other potential regulators prior to making recommendations on their potential use 

in the regulatory setting. 

6. Compliance Assurance 

NESCAUM is aware that many industry stakeholders are interested in developing an alternative 

certification procedure for this NSPS. The NESCAUM states support the current EPA Office of 

Enforcement and Compliance Assurance (OECA) review and certification process, and would not 

support any significant changes or alternatives. If the industry stakeholders have concerns with 
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EPA’s current process, those concerns should be brought to EPA’s attention and addressed; they 

should not be the basis for eliminating the certification process and moving to an unproven program 

for emission standards verification. EPA is required to ensure compliance with its regulations. 

Given the current economic situation and states’ resource constraints, such proven programs are 

needed now, more than ever. In addition, the NESCAUM states are deeply concerned about the lack 

of oversight and follow-up on testing of units as defined in the current NSPS. Therefore, 

NESCAUM strongly urges that EPA provide additional resources and oversight for this program in 

the future. 

Recommendations 

• Continue with the process of OECA review and approval of certifications. 

• Work with manufacturers to address concerns. 

• Only allow third party processes for voluntary programs, and audit results to determine their 

effectiveness. 

• Incorporate electronic reporting and streamline efforts for providing data to EPA to increase 

the efficiency of program oversight. 

• Increase OECA’s oversight and audit efforts for this rule. 

7. Determining the Levels of the Standards

The NESCAUM states fully support EPA’s efforts to look at technology and emission levels 

throughout the world. NESCAUM encourages EPA to review and determine Best Demonstrated 

Technology (BDT) levels in Europe, where lower emission standards have resulted in significant 

improvements in emissions performance. 

8. Consistent and Protective Forms of the Standards 

NESCAUM supports use of a common metric across the variety of devices that would be regulated 

under this program. A common standard metric, combined with a common test method, allows the 

consumer to compare emissions performance across different units within a class as well as 

emissions between different types of devices. Furthermore, the NESCAUM states support the use of 

a blended emission standard, such as the one currently used in the NSPS and the one used in EPA’s 

Phase 2 voluntary program for Outdoor Wood-fired Hydronic Heaters. A blended standard that 

combines pollution generated by heat delivered along with the amount of pollution over a unit of 

time allows not only for a comparison of emissions based on heat delivered, but also, more 

importantly, the measured mass emitted over time. This can allow EPA to model emissions and 

develop standards that ensure that public exposures will be minimized regardless of the device type. 

Given that these units are placed in residential situations, and there may be multiple units in a local 

airshed, it is critical that EPA develop emission standards that ensure, at minimum, that the public 

will not be exposed to unhealthy air pollution levels. NESCAUM therefore recommends that EPA 

conduct a modeling assessment to ensure that a revised emission standard will not result in local 

exposures at levels above a National Ambient Air Quality Standard (NAAQS). Given recent 

movement towards incentives for energy efficient units so that wood is not being wasted, the 

NESCAUM states also urge EPA to develop a standardized efficiency test method and a performance 

level under a revised NSPS. 
6

Recommendations 

• Use a common metric for emission standards across device types.

• Use a hybrid emission standard that incorporates pollution generated per unit of heat 

delivered and pollution generated over a period of time.

• Ensure that standards will not result in exposures above a NAAQS.

• Develop a standardized efficiency test within the revised NSPS.

• Establish (separate) minimum performance standards for combustion efficiency and for heat 

delivery. 

9. Current Inventory

One the largest challenges faced by state agencies are the emissions from the current inventory of 

residential wood burning devices, which include unregulated devices and pre-NSPS woodstoves. 

NESCAUM urges EPA to expand current change-out efforts with respect to the size and scope of the 

targeted devices, such that change-out programs include other residential wood burning devices with 

outmoded technologies. 

If we can provide any additional information or help in any way, please contact myself or our lead 

staff person, Lisa Rector, at 802-899-5306. 

Sincerely, 

Arthur Marin, Executive Director 

NESCAUM 

cc: NESCAUM Directors