Low-cost air quality monitors excel at detecting levels of indoor wood smoke

At $39 - $45, real time PM sensors can empower homeowners – and neighbors 

Ever wonder if your wood stove or pellet stove elevates your risk of inhaling particles that could endanger your health?   Recent advances in technology now make indoor air quality monitors small inexpensive and simple for people with wood and pellet stoves - or fireplaces.  The Alliance for Green heat bought and tested several and found the Tempo S1+ Smart Air Quality Monitor is the most versatile, with Govee Smart Air Quality Monitor,  to be a close second.

 

The Govee Air Quality Monitor (right) shows PM, temperature and humidity on a digital display.  The Amazon Smart Quality Monitor on the rleft ($79) only has a small light indicating air quality.

Not all wood and pellet stoves result in poor indoor air quality.  But there is little research that compares different types of wood and pellet stove installations. The human nose is very sensitive and if you smell wood smoke in your home often, that is enough of a reason to look into the problem.  

 

Low-cost sensors like the TemTop S1+, the Govee or the Amazon sensor (that connects to Alexa) detect particulate matter (PM2.5) and can help homeowners better understand the issue and may be a motivating factor to take action, which could mean calling a chimney sweep or just cleaning your pellet stove better before lighting it.  

In the future, such monitors could easily be built into stoves, which could be a significant advance in helping homeowners understand how to best run them.  In 2025, MF Fire plans to introduce an aftermarket sensor package designed to help homeowners operate their stoves better, but they do not measure indoor PM.

Feb. 20. The Govee (left) and Amazon (right) are both easy to set up on your phone and see temperature, humidity, PM and CO on an hourly, daily, weekly or monthly basis. We found they correlated relatively well. They both spiked around 7 PM, cooking dinner but the Amazon did not record much of a morning spike when I lit the stove and cooked breakfast. Both calculated the daily average at exactly 3ug/m3.

On Feb. 19 both the Govee (right) and Amazon (left) monitors caught the morning start-up/breakfast and elevated evening PM.  The Govee had a 2 ug/m3 daily average and the Amazon had a 3 ug/m3 daily average.  One big benefit of the Govee is that is shows temperature on the same screen as PM, and you can see when the pellet stove is turned off around 10PM and turned back on around 6:30 AM. 

 

Digital displays are now everywhere in our homes and cars and they tell us everything from when to add air to our tires to when to change the filter on a furnace.  But for those of us who heat our homes with wood stoves and pellet stoves, the health of our kids and our spouses should be paramount. The EPA also has good information on indoor air monitors.

Another benefit of the Govee is that it pushes a message to your phone, wherever you are, when PM spikes.  At 6:40, just as I was lighting the pellet stove, it briefly spiked to 35 ug/m3, and I got a message on the cellphone when I looked at it, 15 minutes later, at 7:05.  The average on Feb. 21^st was 3 ug/M3.and there was also a little PM elevation around dinner.

 

Low-cost sensors are also useful for neighbors who may be breathing wood smoke from someone else’s wood stove.  When outdoor air quality is bad, it leaks into homes and these sensors can help neighbors talk to each other using data, not emotional reactions, to wood smoke issues.

 

Data from my home’s pellet stove

 

My pellet stove emits a little smoke on start up, but I found that after the first half hour, there is no air quality impact that the sensors could detect. I turn my pellet stove off when we go to bed and when we wake up the sensors usually say the house has 1 µg/m³, meaning 1 microgram per cubic meter of air. By the time the pellets catch fire, it usually reads 6 or 7 ug/m3 but it can also go up to 30 or 40. But if we fry something for dinner, the sensor often goes to 30 or 40, and if we over fry something to the extent you can smell something is nearly burning, the sensor can read 100 or even 200. Our conclusion is that the riskiest behavior in the house is cooking, but your house may be very different, and a wood stove may emit far more indoor smoke than my pellet stove.

 

If I don’t clean the burn pot of my pellet stove, it takes longer for the pellets to light off, and there can be quite a bit of smoke. Currently, I have a Harman Accentra but I had the same problem with a Ravelli.  It appears that the exhaust fan doesn’t go on until the stove sensors fire in the burn pot, but by then the smoke has found any available crack to leak into the room.  This seems like a design flaw, but we all know that positive pressure in a firebox is a recipe for problems.  

 

In our house, we use an older gas stove that is located in the kitchen, about 15 feet away from the PM sensors which were placed just 2 feet away from the pellet stove. Our impression is that regardless of whether you have a gas, electric or induction stove, frying will reduce air quality, particularly at higher temperatures.  We don’t have a exhaust hood or fan above our cook stove, which we presume would be a big help to reduce PM from cooking. A hood with a fan exhausting to the outside may be the best investment in homes that fry food often.

 

Indoor air quality for wood stoves, pellet stoves and fireplaces

Conventional wisdom, based on tens of thousands of wood and pellet stove users, is that indoor smoke is usually far worse with wood stoves.  Part of the problem is that wood stoves need to be reloaded, usually every 1 – 4 hours, and depending on wind conditions outside, how quickly the door is opened, etc. the negative pressure in the firebox is broken, and smoke spills into the room. When a pellet stove is reloaded, you open a door to the hopper, not to the firebox, so there is no impact on pressure in the firebox and no opportunity for smoke leakage. Also, since the exhaust flue is powered by a fan in a much smaller pipe, windy conditions outside are far less likely to impact indoor air quality.

 

An air quality sensor can tell you how bad your indoor air gets when you reload – and crucially – how long it takes to get back to normal. Once you start measuring it, it gives you a metric which can lead to behavior change.

 

With both wood and pellet stoves, improper installation can aggravate or cause leakage of smoke. With pellet stoves, the exhaust pipe has positive pressure and can leak if it's not sealed or installed properly.  With wood stoves, a short exhaust pipe which can often be found in trailers, and self-installed stoves, can lack the suction needed to keep smoke from spilling out into the room.

 

Did I need the sensor to help me understand the relationship between cleaning my firepot better and start-up smoke?  Not necessarily, but it gave me data to measure it on a daily basis, better understanding the solution, and it gave my whole family some reassurance that the stove did not cause much of a problem at all compared to cooking. 

 

How much smoke is acceptable?

It is easy to say that no additional indoor PM is acceptable yet we all live with it when we cook, toast bread and vacuum floors and rugs.  The EPA and the World Health Organization(WHO) say that indoor 24-hour averages should be below 12 – 15 ug/m3, or more recently down to 9 ug/m3. My house, with cooking meals for 3 people and running a pellet stove from 6:30 AM to 10 PM, almost always stayed well under those average limits. However, in homes were a wood stove were to result in daily averages of 20 or more, that would likely be unacceptable to many people, as I think it should be.  Learning when and how to reload your stove quickly and efficiently may help.

 

In terms of outdoor, ambient wood smoke, we know that concentrations of wood stoves in valleys, especially those with more frequent and severe inversions can pose serious health risks.  I have come to believe that restrictions on the new installation of cord wood stoves in those areas is often a step in the right direction.  Wood stoves are not a good energy solution in any densely populated area, not because they are usually not operated well-enough with dry enough fuel. However, we think pellet stoves can be a far greater energy solution than they are today, and should be allowed to be installed even in areas where cord wood stoves aren’t.

 

The toughest question is how to compare and contrast the additional local PM from wood or pellet stoves and the disastrous global impact that oil and gas heating have.  All renewables are increasingly getting local pushback even in the face of overwhelming data showing we need to ramp up renewables far faster than we have been.

 

What do the academic studies say?

There have been multiple academic studies of indoor PM impact of cord wood stoves but we could not find any about pellet stoves. For wood stoves,  one study found an average of 20% higher PM in homes with wood stoves. Another said that wood stoves triple the PM in a homes. Another found that the age of the wood stove was not a determinant of indoor air pollution but more frequent cleaning of the flue was a factor. This was the same conclusion of a well-known study in British Columbia that found there was not a consistent relationship between stove technology and outdoor or indoor concentrations of PM_2.5. Yet another studyfound higher PM in homes with wood stoves and the primary mechanism for introducing PM into the home was opening the door to the stove.

 

Do air purifiers work for wood smoke?

Yes, air purifiers can be effective for indoor smoke from forest fires, your neighbor’s wood stove, or your own wood stove. AGH began promoting the use of air purifiers in 2015 and since then, the rise of wildfire smoke have made them a commonplace solution.  But if the problem is your own wood stove, you should fix the problem before putting a band-aid on the symptom of the problem.  One of the highest rated air purifiers is  Blueair Blue Pure 211i Max(around $279) or Blueair Blue Pure 211+ (around $169).  Both consistently perform nearly as well or better than more expensive ones. One downside for all air purifiers is the cost of replacement filters ($25 - $35 for Blueair filters) which should be replaced once or twice a year depending on how much you use it and how dirty your air is.

 

Purple Air Sensors

I have used multiple Purple Air sensors extensively but did not include any of the data here in part because they are far more complicated to set up and can be glitchy. They are highly recommended, however, for a wide variety of ambient PM measuring. Data from ours led us to the same conclusion: the pellet stove caused a spike in PM when it started, but air quality returned to the same levels as when the stove was off pretty quickly.  With the Purple Air, we also confirmed that by far the worst events in the house were cooking, not starting or operating the pellet stove. 

In 2019, I set up both indoor and outdoor Purple Air sensors at my house, and my neighbors’ who had a cord wood stove. Sensors with a circle around them are indoor. The data was made public, and of interest to the Purple Air community. 

 

Here the Purple Air sensor at the bottom, mostly in green was indoor and the upper one, mostly in yellow was outdoor. Thus, the 7 PM spike from cooking did not impact outdoor PM, but the stove lighting around 8 AM caused a spike indoor and outdoor. (This is data from 2 units but each unit is a combination of two sensors, and you can see how closely they track each other.) 

 

Use of Govee and Amazon sensors outdoors

The Govee and Amazon sensors are indoor sensors but I was curious to see if they could detect start up smoke of my pellet stove when placed on my front porch, about 25 feet and around a corner from my pellet stove exhaust pipe.  I brought both sensors outside and turned my stove off at 11 AM and turned back on at 4 PM.  The result indicates that outdoor emissions of this pellet stove start-up were not detectable at 25 feet away on a relatively windless day

 

This shows that both the Amazon and Govee monitors did not detect elevated PM2.5 during a pellet stove start-up cycle a 4:00 on Feb. 21 when placed about 25 feet from the pellet stove exhaust pipe. If the sensors were placed directly under the exhaust pipe, the results would be very different, as there is always a strong smell of smoke there.

 

Conclusion

We found that our pellet stove does not significantly impact air quality in our home compared to other daily activities such as cooking and cleaning.  The pellet stove does emit some PM on start-up, but on a daily or hourly average basis, it was usually still well within EPA and WHO recommended limits.

 

If you regularly smell wood smoke in your home, you have a problem and you should not delay in trying to fix it.  A low-cost air sensor can be an excellent way to assess the problem with reliable data, or let you know that you don’t really have much of a problem at all compared to other daily household events like cooking and cleaning. 

If you have a pellet stove that emits some smoke on start-up, or if you have done any air quality monitoring in your house with a wood or pellet stove, please contact us and share you experience.

 

 

10 States sue the EPA to improve wood stoves, but the grounds are dubious

Old stoves removed during change out
programs range from ones like these ...

Ten states and one large air agency filed a notice that they intend to sue the EPA over its weak wood stove testing, certification and enforcement programs. The lawsuit is one of the only ways to keep the agency on the required timeline of updating its wood and pellet heater regulations every eight years. Otherwise, the agency can easily let timelines slip and put wood heater policies and regulations on the back burner as both Republican and Democratic administrations have usually done.

The Alliance for Green Heat (AGH) supports the lawsuit for these reasons: EPA needs to keep focused on this technology and keep doing the testing that can get better test methods and stoves that operate better in the hands of the consumer. Automated wood stoves that use sensors, computer chips and actuators to mix the fuel and the air, like in cars, probably offer the best hope for cleaning up wood stoves. But they may be left out of the next updated regulations, known as New Source Performance Standards (NSPS).

... to stoves that are decrepid
and/or dangerously self-installed.

However, AGH does not agree with much of the faulty narrative that says new stoves are not likely to be cleaner than old stoves. And maybe most worrisome is that the AGs of so many states appear willing to make such claims without citing data to support it. 

Unlike the dynamic around auto emissions, where car manufacturers are pitted against the EPA, in this case all fingers are pointed at the EPA for being too lax. The EPA’s wood heater program has had huge weaknesses and it is an easy target. But it is important to understand that the EPA is not a monolith, and it is the wood heater certification and enforcement programs in Washington that are far more of a problem than the section in North Carolina that does the test methods and change out programs.  

One of the many problems with the filing by 10 state Attorney Generals (AG) is that it is mainly based on a review of the EPA’s certification program done by the State of Alaska and Northeast   States for Coordinated Air Use Management (NESCAUM), with funding from New York State Energy Research and Development Authority (NYSERDA). It is not based on testing of new stoves in the field compared to old, uncertified stoves in the field. The narrative that the EPA has been wasting money on change-outs because new stoves aren’t necessarily cleaner than old ones seems to be gaining traction despite evidence to the contrary. Moreover, it distracts from the real, complex tasks at hand and is divisive. As a public relations strategy, it has been successful, gets good media coverage and rallies liberals.

The reality is far more complex. Ironically, it also misses what blue states care about: maximizing renewable energy in smart ways and creating more equity in the energy transition. Starting with the NESCAUM report, pellet appliances have been sidelined from the narrative and they are not even mentioned at a time when much of America is confused about the difference between premium heating pellets and industrial pellets to make electricity. If wood and pellet stoves are to play a role at helping the US reduce residential fossil fuel and protecting low to moderate income (LMI) households from the high costs of the new energy paradigm, it is vital for AG offices to understand the role of the technology in America. 

The Notice to Sue, likely leading to a lawsuit can be good for our common goals of getting cleaner wood stoves, but AG offices need to understand some things. First, we don’t need a new NSPS before we have new test methods. (One of NESCAUM’s many roles is providing data for new test methods, but compared to other labs, NESCAUM’s lab is way behind schedule, which complicates the whole timeline.) Second, the goal of getting better repeatability of a test result within a lab and between labs does not necessarily lead to a cleaner stove in the hands of homeowners. Third, tilting scales toward hybrid stoves may help in the short run, but is not necessarily a long-term or nationwide solution. Fourth, there has never been much agreement on what constitutes the best systems of emission reduction (BSR) in stoves which hinders the EPA in writing regulations that can force technology to change and improve. 

Wood and pellet heaters can help the nation in our transition to electrification by giving homeowners a back-up heating source, lowering stress on the grid during wintertime and providing LMI households protection from rising electricity costs which helps achieve equity. And environmental justice is improved in poor communities not just by a reduction in woodsmoke but also by improving energy security so that homes do not have to choose between heating and eating. For low-income households, change-out programs have been very important by removing unsafe stoves that pose a fire risk, improving not just ambient particulate matter (PM) and indoor PM, and adding heat pumps to many homes. 

The next NSPS will be best served by an EPA with the budget that enables them to collect their own data and properly manage the certification and enforcement programs, which are still far from effective. Underfunding leaves the EPA vulnerable to just reacting to one side or the other, and making poor decisions like revoking a cordwood test method that should have been changed and improved instead. That revocation was also prompted by the same group of states, most of which lack the expertise to understand the complexities and the politics of such a move. Tightening up that test method would have helped the EPA gather vital data it needs for this NSPS and not rely on data from parties who are sparring for an upper hand in the process.

The mostly blue states leading this lawsuit also need to manage wood and pellet heating far better in their own borders, as all states do. Vermont is a good model which is also heavily promoting heat pumps. States should be promoting pellet stoves and boilers and demanding stricter PM limits for those appliances. They should also limit the new installation of cord wood stoves in densely inhabited areas unless, or until, automation and mini-electrostatic precipitators can make cordwood units far cleaner. While cordwood stoves are essential for rural LMI households and help them get off fossil fuels, manually operated wood stoves are simply not a good energy solution where lots of homes are close together, particularly when the topography leads to frequent inversions, trapping PM close the ground where we breathe. 

As for the solution to reduce wood smoke in Fairbanks, even Albert Einstein would be scratching his head. Managers of that change-out program have done an admirable job and used many different strategies. They also uncovered huge problems in the EPA’s stove certification program which were hiding in plain sight. But we should not expect the next NSPS to make much of a dent in that intractable problem. 

Nationally, the solution lies in far more funding for R&D in stove technology, more attention to enforcement of current regulations, more experts for state AGs to rely on and collaboration. Like many big energy issues, the solutions are multi-faceted and rely on a collaborative approach by stakeholders. We should take this lawsuit as a wake-up call.

Veteran lab technician challenges Alaska's wood stove criteria

Ben Myren, left, with Larry Brockman
at the 2018 Stove Design Challenge
where the IDC was showcased.

Updated, April 2, 2021 - Ben Myren, one of the nation's most experienced wood stove test lab experts, is frustrated with the officials in Alaska that are trying to enact stricter wood stove standards.  Fairbanks has to design a State Implementation Plan (SIP), to clean up their air to meet federal air quality limits or face sanctions. 

Myren is not alone in his opposition to the way Alaska is seeking to crack down on more polluting stoves.  Nineteen entities responded to the EPA's public comment on the Alaska stove requirements and all 19 were very negative.  This is not entirely surprising considering all 19 comments came from the wood stove industry, mainly from manufacturers.  Their comments can be viewed here and Myren's comments are reproduced below.  Companies that commented against the ADEC proposal included HHT, US Stove, Jotul, Rais, Blaze King, Central Boiler and Woodstock Soapstone.

The Alaska Department of Environmental Conservation (ADEC) stove requirements resulted from  a novel and ambitious review of certification reports of all wood stoves. According to its reports, the agency found missing and flawed data in nearly every set of certification papers sent to the EPA by EPA approved testing labs. One of those labs, run by Ben Myren, provided scores of reports ADEC found to be deficient.

Following ADEC's review, the Northeast States for Coordinated Air Use Management (NESCAUM), a non-profit based in Boston, used that data in a scathing report that found the EPA's system of certifying wood and pellet stoves boilers and furnaces to be "dysfunctional." Currently, high level officials at the EPA are reviewing the NESCAUM report and the stove industry and states are waiting to see what parts of the report the EPA will address and how. In the meantime, the EPA has reportedly stopped processing certification paperwork.

The stove industry association, the Hearth, Patio & Barbecue Association (HPBA) dismissed the NESCAUM report in a blog by John Crouch, their Director of Public Affairs, saying they do not see "any indication that the regulatory process doesn't work." Instead, Crouch says that the report is the result of an "anti-woodstove agenda" and its authors are trying to "find a problem so that they can push for their desired outcome." The Alliance for Green Heat's response urged the EPA to "take the report seriously", and calls on the Biden Administration to provide more resources for implementation and enforcement. AGH was critical that the report failed to sufficiently distinguish the far more fair and reliable testing of pellet stoves and boilers, which could undermine important efforts of New England states to incentivize modern pellet heating as a means of reducing fossil fuel reliance.

Myren, and most of the manufacturers who commented objected to virtually all the keys ways Alaska is trying to require stricter standards in their effort to convince the EPA that they are addressing its air pollution non-attainment problem. The EPA accepted Missoula's strategy of simply banning new installations of wood stoves and limiting pellet stove installs to devices emitting 1.0 g/h or less. Missoula's 1.0 g/h limit was also enacted ex post facto, and did not give manufacturers the chance to meet the stricter local standard in advance. Myren notes that Alaska's requirement that stoves not emit more than 6 g/h during the first hour of a test to be sold in Fairbanks is unfair, including because some stoves test with a cold start and capture heavy start-up emissions while others test from a hot start. 

ADEC points out that the strong objections posed in all the industry comments may backfire, because if the EPA rejects ADEC's approach, the fallback may be simply ban the installation of new cord wood stoves, like Missoula did.  The EPA approved Missoula's strategy and ADEC is using that as a yardstick to craft something that may be equally effective at reducing wood smoke, but still allow Fairbanks residents to install more cordwood stoves. 

Myren also found that ADEC appears to be requiring more bark on the test loads of cordwood for the ASTM test than for the Integrated Duty Cycle (IDC) test it asked the EPA to approve. Thus, if a lab uses the IDC method to certify a stove, it may fail ADEC's criteria. If Fairbanks wants a test method that will help identify stoves that will perform well in that polar-like environment, Myren argues that the IDC fails on many counts. In fact, Fairbanks may do better to alter the IDC to test stoves for their ability to burn in sub-zero temperatures, which causes a much higher draft than used in the IDC.

 

MYREN CONSULTING, INC.

AIR PLAN APPROVAL; AK, FAIRBANKS NORTH STAR BOROUGH;

2006 24-HOUR PM_2.5 SERIOUS AREA PLAN

86 FED. REG. 10,511 (FEB.22, 2021)

 

     The US EPA is proposing to approve parts of the Alaska State Implementation Plan for the Fairbanks North Star Borough Area (NSSIP).  Part of the NSSIP includes revised emissions standards and, possibly new test methods, for wood stoves.  Myren Consulting, Inc. (MCI) would like to offer the following comments on these proposed actions.

 

     1. EPA’s initial choice of the 2.5 g/h particulate emissions (PM) standard for wood stoves tested with cord wood (the cord wood option, see Section 60.532(c) in the 2015 NSPS) was made without any supporting data that demonstrated that the 2.5 g/h standard related in any way to the crib fuel standard of 2.0 g/h.  (See Section 60.532(b) in the 2015 NSPS.)  In short, EPA never conducted any M301 Validation tests to compare the emissions from the 2 different test methods (EPA M28/ M28R and ASTM E3053) used to determine PM emissions from wood stoves.  Thus, any use of the 2.5 g/h standard in the deliberations that led to the content in the NSSIP is both arbitrary and capricious.

 

            2. The Alaska Department of Environmental Conservation’s (ADEC) choice of a 6.0 g/h PM emission limit has also been made without any similar supporting data.  Thus it is also arbitrary and capricious.  

 

3. The 6.0 g/h PM emission limit is also arbitrary and capricious because it does not differentiate between the two test methods, EPA M28/ M28R and ASTM E3053, presently being used to certify wood stoves.  The operating and fueling protocols in these two test methods are very, very different.  The EPA M28/ M28R requires hot to hot tests for all tests with the crib fuel loads made from dimensional lumber (2x4’s and 4X4’s) that uses a loading density of 7 lbs. ±10%.  ASTM E3053 requires a cold to hot start for the High burn, hot to hot starts for the Medium and Low burns.  The fuel used in ASTM E3053 is cord wood with a loading density of 10 lbs. ±5% for the High burn and 12 lbs. ±5% for the Medium and Low burns.  Just the difference in fuel type (crib fuel vs. cordwood) and loading densities (7 lbs. ±10% vs. 10 lbs. ±5%/ 12 lbs. ±5%) would suggest that the 6.0 g/h limit can not be applied evenly to these two methods. 

 

4. Given the way the stoves burn during these tests, especially for the ASTM E3053 cold start High burn, the 60 minute filter pull 

happens at very different times in terms of what is taking place in the firebox.  On smaller stoves being tested with ASTM E3053, it is very possible that the filter changed at 60 minutes will contain all of the emissions from the cold start (K/S) phase plus a portion, the dirtiest portion that includes coal bed leveling, loading and ignition of the High burn fuel load.  Here again, the failure to differentiate between what is happening in the firebox on stoves of different sizes renders the 6.0 g/h unfair and arbitrary and capricious.

 

5. The same is true for the larger fuel loads required in the ASTM E3053 tests, i.e., higher loading densities means larger/heavier fuel loads, which take longer to ignite, so the emissions will understandably be higher during the first 60 minutes.  Again no differentiation, which is unfair, arbitrary and capricious.

 

     6. The 6.0 g/h 60 minute PM emission limit is being applied in an ex post facto manner.  Had manufacturer’s known about this limit in advance, they would have had the opportunity to change their wood stove designs and bring their stoves into compliance.  However, that is not the case with the presently proposed rules because the 6.0 g/h rule is being applied to stoves already certified.  That, again, is grossly unfair, not to mention arbitrary and capricious.  

 

     7. The ADEC’s certification stove review process is horribly skewed, because it requires documents that were never previously required in the EPA certification process.  Here I am referring to the newly required documents titled “Document of Run Appropriateness”, “Document of Run Validity”, “Document of Run Anomalies” and “Document of Run Burn Rates”.  These documents are nothing more than “boilerplate” and do nothing to effect the actual test results.  Again, this is grossly unfair, not to mention arbitrary and capricious. 

 

8. In addition, the ADEC review criteria often establishes other new criteria that, in effect, establish new more stringent criteria that must be met before a stove can obtain ADEC approval.  One of these is the establishment of an undefined requirement for the medium dry burn rate for cord wood stoves.  The question asked in the ADEC’s Summary of Review” in the “Comments” section is essentially, “Why is this Medium primary air control setting representative of what is needed for a Medium burn?”  Yet the data presented show that the dry burn rate in the test report meets the requirement set forth in the test method.  Thus, the ADEC is revising test criteria after the fact.  Again this is grossly unfair, not to mention arbitrary and capricious. 

 

9. Similarly, the ADEC’s Summary of Review for wood stoves certified with cord wood using ASTM E3053 seems have a minimum requirement that at least 50% of one side of each fuel piece be covered with bark.  Yet that 50% requirement clearly contradicts what is found Section 3.29 in the recently approved Integrated Duty Cycle (IDC) test method (EPA Alternate Test Method ALT-140) which states in part:

 

“…Test fuel charge – the collection of test fuel pieces used in   each of the four phases of the test run.  L2, L3, and L4 require that at least 5% of the individual pieces with at least 80% bark on one side of the fuel piece…”  

 

 ASTM E3053 Section 8.4.2.1 states that

 

“…Only cordwood pieces that are free of decay, fungus and

loose bark shall be used…” 

 

Thus there is no “official” bark requirement in the ASTM standard.

 

However, in as much as the ADEC requested approval of the AK version of the IDC contains the above cited bark requirement, it seems hard to believe that the ADEC would require an even more stringent bark requirement for stoves tested with the ASTM test method than is required in the IDC test method the ADEC requested EPA approve.  Or is this, once again, just one more instance of an unfair, arbitrary and capricious decision making process.

 

10. The IDC test method as presently written (Version V7B_2.23.2021 AK IDC) and recently approved by EPA as ALT-140 can not be used as it is written.  Thus any mention of the above cited document in the entire NSSIP document as a means to improve air quality in the North Star Borough is unwarranted.  You can’t cite what you can’t use.  And any use of data generated via testing with the above version of the IDC, or any unapproved version of the IDC for that matter is also invalid, because the test method can’t be used as written.

 

11. Despite claims to the contrary, the IDC test method does not in any way reflect a real world operating scenario.  This is especially true of the Fairbanks North Borough where typical winter subzero temperatures would find homeowners operating their stove with the primary air control (PAC) wide open, not closed to the minimum primary air setting as is required for well over half of the IDC test, i.e., in the IDC test the PAC is set at wide open for the cold start portion of the test and the first 50% of the High burn fuel load weight.  After 50% of the High burn fuel load has been burnt, the PAC must be set to the minimum air setting for the rest of the High burn and all of the Maintenance fire phase, i.e., no additional air is allowed when the Maintenance fire fuel load is loaded into the stove.  The PAC stays at the minimum air setting until the start of the Overnight fire phase, when the PAC can be opened to the maximum setting for the first 10 minutes of a test and then the  PAC must be returned to the minimum air setting and must stay at that setting for the rest of the test.  Does that sound like a typical operating scenario for a stove in the North Star Borough when the outside temperature is less than 10-20 degrees F? 

 

10. If one looks at the entire US in terms of wood burning, Fairbanks is an “outlier” due to the extreme temperatures that occur there.  Thus, the solutions for resolving the air quality issues for Fairbanks may have little or no relevance to resolving air quality issues elsewhere in the US.  EPA needs to recognize this “outlier” status if it should chose to approve any of the suggested proposals to reduce the PM emissions form wood stoves in the Fairbanks area. 

 

11. And lastly, no matter which of the present test methods, i.e., EPA M28/ M28R, ASTM E3053 or the AK IDC, one would decide to use, the stoves certified via that test method will not work well in the field because of the difference in the draft (static pressure (pg)) generated by a freely communicated lab chimney versus the draft that is generated by a real world chimney that vents into the outside air.  Here research has shown that the draft generated by a 28 foot chimney vented into outside air that is 10F can double the dry burn rate of a stove.  Imagine what would happen to the dry burn rate and stove emissions when the outside temperature is -40F.  The Europeans have long recognized this problem and so have induced a draft (12-14 Pa) during their emission testing.  Now they are working on a new test method where the draft is varied over the course of a test run, with the variation in induced draft being determined by 4 different variables, chimney height, outside ambient temperature, flue gas temperature and flue gas static pressure.  Again, failure to recognize the problems with existing test methods and try to eliminate one or more in favor a perceived “better” method ignores reality.  Especially when no actual field testing ahs been done to validate these assumptions, which renders any preference for a particular test method arbitrary and capricious.  

 

In conclusion, many of the criteria the ADEC wished EPA to approve are not based upon scientific data and facts, but instead are simply an arbitrary and capricious choice. 

 

Thank you for the opportunity to present this testimony.

 

Ben Myren, President

Myren Consulting, Inc.

512 Williams Lake Road

Colville, WA 99114

email: <myren.ben@gmail.com>

Related stories

Alaska releases deficiency details on wood and pellet stove test reports (Nov. 2020)

AGH response to NESCAUM report on data from Alaska process (March 2021)

Alaska building list of cleaner, properly certified wood and pellet stoves (Oct. 2020)

Alaska releases deficiency details on wood and pellet stove test reports

Bryce Ward, Mayor of Fairbanks
North Star Borough.

Alaska posted summary review sheets of nearly every certified wood and pellet stove, exposing issues in a certification system that has been running for decades with little oversight. Of the 131 wood stove models, 130 had major problems in their testing report based on the Alaska classification system.

ADEC is pursuing EPA approval of s smoke reduction plan similar to one in Montana. They said, “Missoula City-County Montana regulations allows installation permits only for pellet stoves emitting no more than 1.0 gm/hr.  Alaska embarked on the certification test review and the establishment of a 1-hr filter pull standard as an alternative to a pellet only program for the nonattainment area as DEC feels this approach meets the communities desire for more device options and is at least equal to the Missoula requirement."  Click here for the full email.)

Alaska also sought and received approval from the EPA for an IDC cordwood stove test method to be "broadly applicable" which means any manufacturer can choose to use it in a stove's certification test. It also sets the stage for Alaska to potentially require that test for stoves sold in Fairbanks.

Alaska is undertaking this unprecedented review in an effort to find the stoves that they can be assured are the cleanest and meet all the requirements in EPA regulations under the Clean Air Act. AGH first covered this in a October 22 blog. In addition to checking that stoves meet the extremely detailed level of documentation based on emission testing, Alaska has imposed even stricter emission requirements, which do not apply anywhere other than Fairbanks. The primary stricter standard is that stoves cannot emit more than 6 grams an hour of particulates during the first hour of a multi hour test. Ultimately, when averaging the PM of the entire test, stoves must emit no more than 2 grams an hour to meet the Fairbanks standard, even though the federal standard allows up to 2.5 grams of PM if a stove is tested with cordwood.

Part of ADECs summary sheet showing
 the preliminary and initial final
determination and the reasons.

The initiative is being undertaken by the Alaska Department of Environmental Conservation (ADEC). It only impacts which stoves and boilers can be installed in a relatively small area around the city of Fairbanks that currently fails federal air quality limits. That is a very small market for the wood stove industry but the initiative may end up having far reaching implications for the EPA, the stove industry and how stoves are tested in the future.

 

One reason why so many stove models are flagged with multiple deficiencies is simply because ADEC officials missed data in the test reports or the manufacturer of the model has not yet provided it. Of the 130 stoves with major problems, many will likely meet Alaska’s review in the coming months. Manufacturers who have requested an extension from the State have until April 1 to work with Alaska to provide details, and only after that can the model not be sold in the Fairbanks non-attainment area. In the meantime, the review appears to shpow that only one wood stove model – MF Fire’s Nova tested by ClearStak lab – could be on the market. The data sheets on all stove models can be found here and will be updated at least monthly.

A Step 1 Jotul stove being tested by
Dirigo labs, taken over by PFS-Teco.

The data on pellet stoves is far better in some respects. Rarely do pellet stoves emit more than 6 grams during the first hour of a test like many wood stoves do. Of the 97 certified pellet stoves, only 3, or about 3%, are disqualified for this reason, compared to 31% of wood stoves. However, like wood stoves, the vast majority of pellet stove test reports had missing data. Only 7 had minor issues. As with wood stoves, over the ensuing months, scores more will likely be approved after missing information is found or provided by the manufacturer. Eleven of the test reports could not be found by ADEC. Sometimes links to these reports are hard to find, sometimes the link is broken, and sometimes the report doesn’t appear to be posted.

ADEC has not yet determined which missing items on test lab reports disqualify a stove. Some of the issues ADEC is flagging have to do more with paperwork requirements than the potential cleanliness of the stove. They are engaging in a series of meetings with EPA personnel from both enforcement (OECA) and air quality (OAQPS) offices to determine what is actually required by the NSPS, what isn’t required, and what should be considered significant. One long time technician at an EPA approved lab said that “based upon ADEC’s interpretation of the language in parts of the Federal Register, they have come up with several new requirements” which never existed before.

A 2019 pie chart made by AGH
showing an approximate percent
of stoves tested by each lab based 
on one data set.

For manufacturers, a key distinction is also data that was collected and exists, but was never calculated or reported properly, compared to data that was mistakenly not collected and could only be obtained by retesting the unit. It’s unclear if any of the test reports are so deficient that the EPA would ever considering revoking a certificate.

The scrutiny of certification paperwork by labs by Alaska also comes on the heels of years of effort by the stove industry to prevent stricter emission standards and the possibility of stricter audits. States have become increasingly frustrated that the EPA is not enforcing their regulations governing wood stoves and boilers. While enforcement was explicitly curtailed under the Trump administration, under Obama and previous administrations, enforcement has been regarded as lax or sporadic. In particular, the EPA has never initiated an audit of a wood stove or boiler to determine if it can achieve the emission levels that it got on its initial certification test. There is also no documentation of the EPA denying certification of a stove or boiler based on inadequate lab reports. In addition, there are only a handful of documented cases when a stove or boiler has failed emission tests in a lab even though industry cites very high rates of variability in emissions during testing.

Some of these issues emerged in 2019 when the EPA released hundreds of documents that NESCAUM had requested in a Freedom of Information Act request. But very little has ever been written about the many complex and opaque issues in test labs other than a blog AGH posted in August 2019: Records reveal successes and challenges in laboratory wood heater testing. That article explored issues of conflicts of interest, compliance with testing regulations and suspension of certification tests, all of which are receiving are receiving more scrutiny by ADEC officials and their partner agencies.

 

An ASTM 3053 test at Omni lab in
May 2020 on a GHP Group stove. GHP
is a company that has not 
requested that ADEC review its stoves.

ADEC’s initiative is also intertwined with concerns about the ASTM E3053 cordwood method and lab tests that showed the method was lax and may have helped some stoves to achieve certification to the EPA’s stricter 2020 standards with few or no modifications to their design. A meeting between EPA and state officials and industry representatives in January of 2020 explored these concerns and ADEC presented their strategy at that time.

ADECs efforts to improve air quality in the Fairbanks non-attainment area go back at least 10 years, starting with traditional stove and boiler change-out programs and a variety of restrictions. But the tenacity of excessive wood smoke in America’s coldest city has frustrated residents and officials alike, leading to this latest effort to understand which stoves are actually cleaner than others. Fairbanks is also spearheading solutions for the other most obvious culprit: unseasoned wood. As of October 1, 2021, only seasoned firewood can be sold in the non-attainment area.

Registration for firewood retailers is
compulsory in Fairbanks and voluntary
in the rest of the state.

It is still too early to tell how much this latest initiative will lead to cleaner air in Fairbanks. There is little doubt that it will bring a new level of scrutiny and integrity to test reports submitted to the EPA, and help the EPA and state agencies better understand how to craft a federal reference method for testing stoves with cordwood.

Postscript: In March 2021, NESCAUM released a report that was largely based off of the reviews of certification reports done jointly by ADEC and NESCAUM.  The scathing report concluded that the EPA process of certifying stoves is "dysfunctional" and recommended a series of aggressive measures.  AGH's initial response that report can be found here.

Related stories

Veteran lab technician challenges Alaska's wood stove criteria (March 2021)

Alaska building list of cleaner, properly certified wood and pellet stoves (Oct. 2020)

Alaska building list of properly certified wood and pellet stoves

Lab certification test are designed to
burn as cleanly as possible and all
emission results must now be publicly
disclosed as of 2015.

Alaska Finds widespread deficiencies in EPA wood stove certification process 

Officials in Alaska are in the process of compiling lists of wood stoves and boilers that have met all the requirements of EPA certification and emit fewer particulates during the first hour of the test burn. Alaska regulations requires new wood heating appliances installed in the Fairbanks nonattainment area to meet additional regulatory requirements beyond obtaining a federal U.S. EPA certification. The regulations went into effect January 8, 2020 and Alaska has been working to implement those regulations since then.  The new regulatory requirements involve reviewing certification test reports for deficiencies and collected data regarding additional PM levels and then approve specific models of wood stoves and pellet stoves by updating their approved device list.

The Alaska Department of Environmental Conservation (ADEC) began this process as part of their efforts to address excess wood smoke pollution that contributed to Fairbanks becoming a non-attainment area.  The State’s Implementation Plan (SIP) to improve air quality began including measures years ago to crack down on dirtier wood burning appliances, such as outdoor wood boilers.

The current effort involves reviewing every stove’s certification paperwork to ensure that it includes all the elements that EPA regulations require, such as average CO, the manufacturer’s written instructions to the lab, firebox dimensions, efficiency calculations, burn rate calculations, raw data sheets, documentation of run anomalies, etc. etc. 

 

If you are not familiar with this brewing controversial initiative, you are not alone.  The first time most people outside a small group of manufacturers and regulators heard about this was a month ago, Sept. 18,  when a group of states weighed in on the litigation between HPBA and the EPA.  Their brief mentioned that the Alaska Department of Environmental Conservation was conducting a systematic review of wood-burning devices that have been certified to be compliant with EPA standards. The Department found that 59% of the certifications had inaccurate certification data, and that the EPA must have a way to check on manufacturers through audits. 

The start-up phase of a stove in the lab
should be consistent with how it is
described in the owner's manual.

The lists being developed by Alaska officials only pertain to what can and can’t be sold in the Fairbanks Nonattainment Area, a very small market.  But regulators, manufacturers and test labs we spoke to all say that this is having major repercussions.  For the EPA, it’s a wakeup call that they have not been sufficiently reviewing test lab reports before certifying stoves.  Test labs are under more scrutiny for various practices and are already  being asked by manufacturers to help ensure their tests come in under 6 grams during the first hour.  And scores of manufacturers are scurrying to provide additional information to Alaska and showing them the details that were in their test reports that Alaska officials missed.  

 

One of the main reasons that everyone is paying attention is that most of the people AGH spoke to agree that other states and change out programs could adopt the Alaska lists instead of using the full EPA list of certified heaters.  If more change-out programs, or even states adopt these stricter requirements, the efforts of a small city in Alaska will have greater national ramifications.  Some managers of change out programs that AGH spoke to say they interested to explore ways to identify cleaner cord wood stoves and are uncertain whether the EPA’s reduction from a de facto 4.5 to 2 grams an hour actually resulted in cleaner cord wood stoves. Incentive and change out programs often have adopted stricter efficiency and/or emission requirements and this may represent the next vehicle for those programs to guide how taxpayer dollars should best be used.

 

The last time state regulators made changes that went on to have national implications may have been in 1995 when Washington State adopted a 4.5 gram an hour state standard, when the EPA allowed up to 7.5 grams an hour.  The 4.5 gram an hour limit soon became a de facto national standard and 20 years later, HPBA insisted it was still the lowest that the EPA should go for the 2015 NSPS.  

Non-confidential portions of emission
test reports made the Alaska investigation
possible for the first time.

Aside from developing new lists of stoves that met all the requirements of the NSPS and emitted less than 6 grams for the first hour of all their certification test runs, Alaska is providing a wealth of information to the EPA, NESCAUM and others who are already in the process of developing a new federal reference test method for certifying wood stoves.  Some regulators the Alliance for Green Heat (AGH) spoke to now acknowledge that they see the current system as “broken” and that no one knew it was so broken.  On November 16, Alaska will be making its data public, showing which requirements in the stove certification process are most commonly ignored or overlooked and which ones are complied with.  

 

The data to be released on Nov. 16 includes a two-page data sheet on individual stoves, showing any deficiencies in their test lab reports.   Each manufacturer will have had up to 2 months to review their own sheets and provide corrections to ADEC prior to their public release.  The initial sheets prepared by ADEC have numerous mistakes according to several manufactures AGH spoke to and include many of the data points that ADEC initially said were not in their test report.  Test labs have been helping manufacturers find relevant data in their test reports, and ADEC will continue making corrections before and after Nov. 16.

 

It’s not yet clear if any test lab reports may be so deficient that the EPA could revoke their certification or require that the stove be tested again.  EPA officials are just beginning to grapple with how widespread the problems may be and what they can do moving forward to help fix problems that should have been in plain sight for so long. The EPA has identified and tried to correct some testing deficiencies in the past.  An AGH blog in July 2019 covered an EPA memo asking labs to correct lapses in reports on stoves tested with the ASTM E3053 test method.  This incident may have contributed to greater scrutiny by states including Alaska’s far more in-depth investigation.

An ADEC official taking
air quality readings on top
of a school.

The EPA certifies stoves based on the weighted average of the entire burn but requires labs to also report the amount of PM in the first hour.  Like efficiency, its data that must be collected and reported by the lab to the EPA, but there is no regulatory limit.  The Alaska initiative is making everyone ask whether the first hour of emissions may be an equally important indicator of a stoves cleanliness than the entire burn cycle.  

 

Currently, the way EPA approved test labs test stoves is by using the standard Method 28 or a variation of it. Lab technicians load stoves with an amount of wood based on the size of the firebox and let the fire go until all the wood is burned, which usually takes anywhere from 4 – 9 hours but can be longer.  During the last several hours of the burn, known as the “tail”, there is virtually no particulate matter being released, but those hours are still averaged into the overall calculation, with much be less than 2 grams an hour with cribs, or 2.5 grams an hour with cordwood. 

 

AGH reviewed scores of test reports and found that single PM reading from the first hour could be as high as 20 grams an hour and the average of all the first hour burns could be as high as 10 grams an hour, but it would be less than 2 grams when the cleaner parts of the burn and especially the tail end of the burn was included.  For Alaska, if any single run went over 6 grams, it was rejected.  Since start-up is the dirtiest part of the burn, identifying stoves that have cleaner start-up may help airsheds improve air quality.

 

Test labs that AGH spoke to noted that this will likely have the result of disqualifying a greater proportion of larger fireboxes.  The average firebox size is 2.2 cubic feet and an initial small sample of stoves with average first hour emissions over 6 grams was 3 grams an hour.  One test lab also said that this could disadvantage catalytic stoves that have no secondary combustion during start up prior to engaging the catalyst, which often occurs 20 – 30 minutes after lighting the fire.  Hybrid stoves, however, that use both air tubes and a catalyst are likely to have cleaner start-up, according to test labs.

 

Some manufacturers are angry that a state is using a brand-new emission metric – first hour emissions – that they could have designed for, if they knew it would be used in some markets to regulate stoves.  Now that it has been flagged, manufacturers certifying stoves going forward can try to meet that – or at least urge the lab to build  the type of start-up fire that will come in under 6 grams.  One of the primary goals of a lab is to familiarize themselves with the stove being tested so they can “optimize stove operations during certification testing.” Some regulators fear that this will just become another factor that manufacturers and labs will use to “game the system.”

 

The Alaska initiative will have a far greater impact on wood stoves than pellet stoves.  Extremely few pellet stoves emit more than 6 grams in their first hour and the testing regimen is more straightforward.  Ultimately, only a dozen or fewer pellet stoves may be disqualified by their review, out of the 98 models that are currently certified. Of the 144 currently certified wood stoves, up to a quarter to a third could be impacted.   New outdoor wood boilers are not allowed in Fairbanks already.  They will be reviewing pellet boilers for compliance.

An inversion in Fairbanks that traps
wood smoke close to the ground.,

Next steps

 

As of Nov. 16, Alaska will publish its review on virtually every EPA certified stoves.  On December 1, only those stoves that ADEC found had complete test reports will remain on the approved device list and be allowed to be sold in Fairbanks.  If a manufacturer needs more time to address potential report deficiencies, they can contact ADEC and if they commit to working to correct the deficiencies, their device may remain on the approved device list.  The first hour emission of 6 grams on each test run requirement, went into effect on September 1, 2020, and those devices have already been removed from the approved device list. 

 

Other jurisdictions, incentive and change-out programs will likely begin assessing whether the Alaska list represents better stoves for public funding.  Consumers who really care about a cleaner stove could also check that list before buying a stove.  For now, there are more questions than answers but the bottom line for everyone in the industry and the wider renewable heating community is that this is a story to watch.

Related stories

Veteran lab technician challenges Alaska's wood stove criteria (March 2021)

Alaska releases deficiency details on wood and pellet stove test reports (Nov. 2020)