EPA reverts to stricter wood stove testing

Agency scuttles one problematic test method, while backing another

The EPA announced that it was withdrawing the most commonly used test methods to certify wood stoves to EPA emission standards.  Those methods, ALT-125 and ALT-127, were developed by an ASTM committee and were the first ever designed to certify wood stoves using cordwood, instead of 2x4s and 4x4s, known as “cribs.” 

To hasten the transition from crib testing to cordwood testing, the EPA allowed cordwood tests to meet a looser 2.5-gram ceiling on particulate matter instead of 2.0 grams with cribs.  The protocol quickly gained favor with stove manufacturers as it was easier to meet the EPA threshold for fine particles in wood smoke.

By withdrawing those methods, the majority of stoves will have to be retested over the next 5 years with a different method, an expensive and time-intensive process for manufacturers.  Normally, the EPA rubber-stamps waivers from retesting for stove certifications every 5 years, and manufacturers have come to expect that, potentially allowing them to sell the same model for decades based on the original certification testing.

The EPA will honor certification tests using ALT-125 or ALT-127 completed prior to Feb. 23, 2022, the effective date for withdrawal of these alternative test methods.  The EPA released details of the withdrawal were released Jan. 21 and will appear in the Federal Register on Jan. 24, 2022.

Nine states had petitioned the EPA to withdraw ALT-125 and 127.  The EPA summarized the reasons cited by the states, saying the “method allows far too much flexibility within the methodology, such that a test lab can ‘explore’ in its testing to find approaches for passing any appliance, regardless of design, ultimately resulting in a certification program where a manufacturer simply pays the lab to provide a passing test, rather than to measure the actual emissions from their appliance without such positioning.”

Crib testing, on the right has been 
used since 1988 to certify stoves.
ALT-125 and 127 used the more
realistic fuel, cordwood, on the left.

The agency is standing behind another problematic test protocol, ALT-140, indicating a trend of approving test protocols before it sufficiently understands and reviews the data that supports them. Tom Morrissey, head of Woodstock Soapstone, studied the ALT-140 method and says it is “unusable” in its current condition and blasts the EPA for approving a method designed in secrecy and does not disclose underlying data.

The EPA’s move is part of a multi-year trend of EPA relying more on the expertise and data developed by air quality groups, and less on the expertise and data from the main industry association, the Hearth, Patio and Barbecue Association (HPBA). The EPA appears to have been approving alternative methods before they have been used to certify stove models based on the work of the stakeholder group that wants the approval of the test method.

The withdrawal will involve manufacturers going back to testing with cribs after making the much-heralded transition to using cordwood, which is what homeowners use. The ALT-140 test method uses cord wood but no manufacturer has used it and none are likely to use it, based on the more secretive way that it was developed and lack of data showing that it works.  ALT-140 was developed by NESCAUM through funding from NYSERDA and sources say that NYSERDA may not be allowing release of the data, even to the EPA.

Morrissey included this image to 
illustrate his analysis of ALT-140

Tom Morrissey released a paper accusing the EPA of a “bait and switch” tactic by approving a method that allowed a higher particulate matter threshold and then revoking it.  Many manufacturers consider the underlying ASTM method sound but concede that the method could be tightened up to reduce its flexibility, rather than revoking it.  A manufacturer could still tighten up the ASTM method and try to get the EPA to accept it again, but that can be a long, expensive and uncertain process.  It is not uncommon for the EPA to revise methods and it is highly likely that ALT-140 will have to be revised.

The EPA approved the ASTM protocol for certifying wood stoves in 2018 after a lengthy and transparent 4-year development process by an ASTM committee dominated by industry insiders.  Many EPA and state officials were part of that process, but few had voting rights. Most were monitoring the process from the sidelines, and few had any background in test method development.  The EPA did not conduct any of its own tests to verify the method and NESCAUM was just building its own internal expertise.

 Within a few years, a majority of the stove models sold in the United States and Canada had been certified using the ASTM protocol, instead of the traditional Method 28 protocol that has been in place for decades.  The new ASTM method was being used to meet the stricter 2020 emission standards that required manufacturers to go from 4.5 grams of particulates an hour to 2.5 or less.  Currently, 90 out of 154 wood stoves were tested in EPA approved labs with the ASTM protocol. This rapid shift to cordwood testing began to draw scrutiny as reports emerged from a program run by the State of Alaska and NESCAUM.  Other reports emerged that some stoves did not have to change their design to cut their PM emissions in half, if they used the ASTM method. 

The intensive scrutiny from the state of Alaska found scores of deficiencies in most test reports, sending shock waves through the industry and the EPA offices that should have caught those errors.  In the process, regulators for the first time realized that the ASTM method allowed too much flexibility in key parts of the multi-day testing process.  Shortly after NESCAUM and the State of Alaska released details about the lack of EPA oversight of the stove certification program, the EPA’s Office of Inspector General announced it was conducting an internal investigation of the EPA’s certification program.  The results of that investigation will be made public later this year.