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Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Rules and Regulations ADEC asserted that the current test method for woodstoves that results in the certification value grams of PM2.5
per hour averages emissions over four steady-state runs. The values from each of these runs is an average emission rate over the time it takes to burn 100% of the full load of wood used for each run.
This approach translates into a certification value that is an average of an average. ADEC stated that averaging results multiple times minimizes emission rates, which results in certification values that may vastly under predict actual in-use emission rates and does not reflect the fuel loading events that in field use may occur multiple times per day. Further, ADEC stated that real-time PM2.5
measurements collected from EPA
certification tests have shown that the maximum emission rate occurs within two hours of the test period, and typically, on average, appliances spend approximately 50% of the certification testing time in the period known as the charcoal tail, where virtually no emissions occur, and in some cases filters may experience particulate loss due to warm dry air blowing through the filter. While this test method approach differs from the NSPS for new residential wood heaters, EPA finds ADECs rationale for the revisions to 18
AAC 50.077 is reasonable and a rational attempt to strengthen rules for the residential space heating source category.
With respect to the inclusion of the TEOM measurement requirement, ADEC
states that the goal was to achieve a 1.0
grams per hour emission limit in practice, taking into consideration the variability of emissions when burning cordwood. After reviewing public comments submitted during the States public comment period, ADEC amended the final regulation to provide an alternative to the TEOM test method while still providing what it considered to be an equivalent, if not better, air quality result than a 1.0 grams per hour average emission limit. The final regulation stipulates that manufacturers may provide the TEOM data as ADEC
originally proposed, with the additional specificity that no rolling 60-minute period may exceed 4.0 grams per hour, or alternatively, by utilizing existing EPA certification test data showing that no valid one-hour filter measurement from the certifying report to EPA is greater than 6.0 grams per hour.
ADEC asserted that, while this limit is three times the final ADEC standard certification value of 2.0 grams per hour or less, the limit will apply to all woodstoves being installed, reinstalled, sold, leased, distributed, or conveyed in
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the nonattainment area not just noncatalytic devices. Due to a number of devices expected to exceed this limit based on the revised test method, the result will be fewer devices available for installation, sale, lease, distribution, or conveyance in the area. ADEC noted this approach is designed to ensure that performance of the devices under more real-world operations will be more consistent because the emissions limit value is not an average. As an example, ADEC found devices that meet the 1.0
grams per hour emissions limit adopted in Missoula County, Montana, but that exceed the one-hour filter measurement of 6.0 grams per hour.
Further, ADEC noted that, while the TEOM is a new approach for wood heater device certification testing, it has been incorporated into a standard test method ASTM D683111 for stack gas testing. ADEC believes the TEOM test is a valuable tool that should be used in future device certification test requirements and has maintained it as one option for meeting testing requirements in the final regulation.
ADEC stated that it is specifying use of the TEOM and its alternative one-hour filter measurement is based on the ADECs analysis of over 60 EPA
approved certification reports, the vast majority of the tests reviewed were for EPA Step 2 certification.
Thus, Alaska developed and implemented additional requirements for wood-fired heating devices, a 2.0
grams per hour limit for all wood-fired devices and hourly requirements measured by a TEOM device or during the EPA certification process, with the intention to reduce the emissions from the home heating source category, the source category with the highest PM2.5
emissions in the Fairbanks PM2.5
Nonattainment Area. EPA has determined that Alaskas revisions to 18
AAC 50.077 are reasonable and strengthen the SIP with respect to the regulation of emissions from the residential space heating source category.
Comment 2: HPBA, Kozy Heat Fireplaces, and Travis Industries assert that the one-hour filter alternative is not compatible with woodstove emissions and the Federal air quality standard that the EPA based on data averaged over 24
hours, noting that the Federal air quality standard is not a peaking standard that is violated by a single episodic, one-hour reading. Thus, the commenters assert that the EPA was proposing to approve this metric without any explanation in the record of its relevance to the nonattainment issues experienced in the Fairbanks PM2.5
Nonattainment Area.

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Response 2: The EPA disagrees with the commenters. First, the EPA
disagrees with the commenters assertion that device requirements must be directly tied to the Federal air quality standard. Overall, the EPA notes that PM2.5 is a complex and highly variable mixture of particles and gases. The EPAs PM2.5 Implementation Rule 81
FR 58010, August 24, 2016
recommends that states should base potential control measures in part on an analysis of emissions inventory data summaries, fine particle speciation monitoring data, and source apportionment air quality modeling data. Emissions standards can have different averaging periods based on the type of source, rate of emissions, and control measure. Irrespective of the particular NAAQS, our basis for approval here is that Alaskas revisions to 18 AAC 50.077 render the SIP more stringent than the prior approved rule in terms of regulating emissions from woodstoves. The EPA finds that ADECs rationale for why the revised 18 AAC
50.077 will reduce emissions from the residential home heating source category is reasonable.
Second, the record contains ample information showing that ADECs revised rule will reduce emissions of direct PM2.5 from the residential home heating source category. The EPA
evaluated ADECs SIP submission, including the responses to similar comments in the development of the States regulation. In ADECs Response to Comments, ADEC noted that, under the 2015 NSPS for new residential wood heaters, the EPA required reporting of emission rates for the first hour of the test period. This data reflects the timing and emission rates typically associated with the 60-minute test requirements for particulate matter testing at all other sources EPA Method 5. ADEC asserted that the assessment of one-hour data allows agencies to gauge performance and determine which appliances are low emitting from the start of the certification test versus those that have been able to design for long charcoal tails to minimize the peak emissions.
ADEC additionally stated that one of the reasons for requiring the use of TEOM
measurement data is to provide a more meaningful equivalency to a 1.0 grams per hour average emission limit as adopted by Missoula County, Montana, taking into consideration the variability of emissions when burning cordwood, while still allowing a range of devices to be sold and used in the Fairbanks PM2.5 Nonattainment Area. Thus, the record does contain information
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