Wood stove use and health

[DBoon]

Yes, our house is leaky or "self ventilating" as we call it.

As are most houses. Mine is pretty rare in this regard because I performed all of the air-sealing details myself and specified redundant air sealing layers in the design/construction. It performs exactly as intended (air is exchanged efficiently and sufficiently to keep the house well-ventilated for occupants) BUT it doesn't have excess leakage/ventilation to cope well with an emitting source (e.g., the stove burning less than optimally dried wood).

I have a good burn going this morning - wood was nice and dry, fire took off easily and rose to 500 degrees F (stovetop) in an hour, emitted no PM2.5 during the active burn, and has low VOCs - all supporting my observations about the root cause of the VOC emissions issues.

 

[John Lehet]

I’ve been looking into air quality measuring instruments a bit. I find a lot of agreement around a lack of confidence in consumer grade VOC measuring sensors, or at least in the absolute reading of a momentary measurement. In other words, their measurements are all relative, if I understand it correctly.

One unit I found that is less expensive and uses high quality sensors is available as a quick-to-build kit at almost half price of the assembled unit. Kit is $138. This one: https://www.airgradient.com/indoor/
That one does not include radon though.

 

[Eman85]

I would go for a model, which will not trap you into buying expensive replacement filters.

It is a little bit like the consumer PC printer market. You buy a cheap printer and get ripped off on the toner.

This was the most confusing thing about looking at air purifiers. The replacement filters pricing and availability.

 

[DBoon]

I find a lot of agreement around a lack of confidence in consumer grade VOC measuring sensors, or at least in the absolute reading of a momentary measurement. In other words, their measurements are all relative, if I understand it correctly.

No doubt that these instruments are not as accurate as something used in industry that costs thousands of dollars more. But do they provide "accurate enough" information to let you know whether something is going very wrong in your environment? My experience is that they do.

 

[Nordicbynature]

No doubt that these instruments are not as accurate as something used in industry that costs thousands of dollars more. But do they provide "accurate enough" information to let you know whether something is going very wrong in your environment?

Ikea has devices for measuring air quality. The sensor itself is manufacturered by Sensirion, a Swiss manufacturer. They are known for being accurate. They are a bargain.

Some Ikea air quality devices only show colours green, yellow, red. But by hooking them up to home assistant you can actually read out the underlying true values.

 

[Raddler]

I’m wondering where the VOC is coming from while the stove is burning? Is it coming out during loading, or somehow leaking out of the stove?

Are we sure the VOCs aren't coming from the stove paint and/or some of the adhesives used in gaskets, etc.? I've been wondering about this myself.

 

[DBoon]

They are known for being accurate.

In case anyone misconstrued my previous comment - I am not saying that home-grade VOC sensors are inaccurate, but they are not traceable to some standard and cannot be calibrated. If I were to use my sensor data to prove a case in a court of law, it wouId not be credible or even admissible in court. Something that was traceable and calibrated would cost a lot more. However, I think it is accurate and provides me with the information I need.

Are we sure the VOCs aren't coming from the stove paint and/or some of the adhesives used in gaskets, etc.? I've been wondering about this myself.

That's a great question. The sensor I have doesn't give me any understanding of what the makeup of the VOCs actually are.

The stove has been well-cured at this point - there is no reason to suspect that paint or gaskets are off-gassing. The signature points clearly to the wood. And to be clear - I am not blaming the stove.

In fact, the VOCs could be coming from anything - non-stove interior product emissions (e.g., recently dry-cleaned clothes, formaldehyde from building products, etc.), from cooking activities, or from ripening/rotting foods. I've learned to recognize the signatures of other non-stove activities, and can separate that out from my readings.

Therefore, I have a pretty good handle on which VOC increases are caused by the stove and which are not. Some VOCs (i.e. from organic decomposition) I would not consider harmful. Others (from wood combustion) I do consider harmful at high enough levels for long enough periods and to be avoided, if possible.

I have been observing the VOC data over a long period of time to gain some understanding of the VOC signatures of various seasons and conditions. I know that my house has a <100 ppb VOC level by itself (which is quite good).

• There is an Amish steam sawmill about 3/4 of a mile south of me and down a hill - when I have a warm, wetter day (in the 40s, humid or rainy) and the wind is blowing from the south almost directly, my VOCs in the house go up (maybe they add 300-400 ppb to whatever baseline level I already have).
• I can see some early morning, afternoon, and evening pulses of VOC peaks on still air, warm, wetter days that seem to correlate with someone a 1/4 mile away and in the valley (I am just above the valley). They add anywhere from 200-500 ppb to whatever baseline levels I already have, and I can basically correlate it to looking out my front window and seeing their stovepipe smoking pretty well on a reload. The pulse durations are short.
• Sudden warming changes at the end of winter will cause VOC spikes for extended periods of time. I think this is because ground that is frozen is suddenly thawed and organic material in the ground starts to decompose, releasing VOCs.
• If I am cooking something on a higher heat with oil (I have an electric induction cooktop) or maybe with a lot of spices in it, sometimes I get VOC peaks even with the fan on and a kitchen window open. Same with baking something in the oven (I have an electric oven).
• I store winter squash, onions, garlic, shallots, and sweet potatoes over the winter in my basement. I cure squash indoors in the fall before moving it to the basement to store it for the winter. If a squash is going bad during the cure, my indoor VOC levels will spike a lot (maybe 1500-2000 ppb) and it is coming from the bad squash (which is sometimes hard to locate for another day or two until the mold appears). The bad squash gets tossed, and VOC levels return to <100 ppb.

The signature of my own wood stove (separated from all of the above, through trial and error) through various burn stages is as follows:

1. No significant or noticeable increase in VOCs during reload - while this may seem counterintuitive, basically there is a lot air going up the chimney at this point and not a lot of wood breakdown into volatile chemicals at this point (there is a small bump in PM2.5, usually). Pattern holds whether door is open for a little longer than normal (i.e., door open to let in a little air during reload doesn't do anything to VOC levels)
2. VOCs start to increase just before the active burn finishes (no more flaming, cat combustor fading to light orange, or orange only in a small part, or black everywhere). I can literally look at the slope of the VOC curve and predict in 10 minutes that the active burn will be over. That is usually when I now open the pipe damper (if it has been closed). If the burn startup was problematic (i.e., took a long time to reach cat combustion so wood likely a little wet) then I will probably open the air a little bit at this point as well.
3. As the stove reaches the coaling phase, the VOCs start to increase and peak about 2 hours after the active burn has finished. Then they level out for 2-3 hours (depending on wood species). For info, it takes about 3 hours for my heat-recovery ventilator to completely change all the air in the house once.
4. VOCs decrease at the end of the coaling (coals burned down) OR stay elevated AND/OR have a second bump up in VOC levels (probably due to a piece of wood shifting and opening new surfaces for combustion).

Other observations:

1. Use of pipe damper doesn't seem to have any impact (surprising to me) as long as I open it fully at the end of the active burn.
2. Lower flue pipe temperatures probably mean less draft and therefore more likelihood that VOCs are staying in the stove longer and getting out somewhere (through gaskets, or through the flue pipe connections).
3. The denser the wood (e.g. hickory) the more VOCs I'll have at peak and the longer the peak will take to return to normal levels. Not surprising - more weight = more volatiles.

For a load with wood that is optimally dry, then stage 1 has zero increase in VOCs, stage 2 will have a very slight slope and lasts longer, stage 3 might mean a VOC peak of only 250-350 ppb (very acceptable to me) for a shorter time, and stage 4 shows the VOC decrease back down to ~100 ppb by time of next reload (usually 9-10 hours into a 12 hour burn/reload cycle).

For a load with some wood that is not optimally dry (but not 1-year wood or obviously wood I should not burn), the stage 1 might show a VOC increase to 250-300 ppb, then stage 2 has a steep slope, stage 3 might peak at 1000 ppb, and stage 4 might decrease slowly or not at all and/or may have a bump in the VOCs late in the coaling and VOCs will not return to house background levels of ~100 ppb. I attribute this signature to wood that is not really ready for coaling by the time the active burn has completed and it is smoldering. In fact, I can look into the stove and see pieces of wood that are well-charred and coaled, but not falling apart (still together). To me, this is a sign of wood that still had too much moisture in the far interior of the wood and that moisture meant incomplete combustion during the active burn and now smoldering.

This is what I am going to try during the off-season to see if it improves VOC levels during the next burning season.

1. I should have even better wood next year - a) better top covers that don't leak, starting last spring; b) wood spaced farther apart in the stacks: and c) 3-year dried wood in the stacks that never spent any time on the ground). Optimally dry wood should really help the most (my belief).
2. More wood of similar size (meaning some of my really big pieces will get resplit, and maybe redried for another year after that). One piece of wood a lot bigger than all others means its combustion will probably be incomplete when active burn is finished.
3. I am going to remove and reinstall my double-wall black pipe that connects in to the back of the stove and to the double-wall chimney pipe vertical run. Goal is to reduce the horizontal run by 6" (increase the draft on startup and also during late coaling) and get the pipe damper a little closer to the stove. I may even try adding some high-temperature caulk to the the connections (though Selkirk never says this is required in any of their installation manuals).
4. I don't like how not tightly the double-wall black pipe connects to the back of the stove. I will definitely try sealing this better with high temperature caulk. This is probably a no-brainer and I should have done this before.
5. I read something from someone (Todd, or BeGreen maybe?) in a different post about using some sort of soapstone dust mix to create a flexible mortar for the joints on the inside of the stove. I'll probably try that also.
6. I am going to buy a manometer to measure the balance of my HRV system. I suspect that it is also not balanced correctly and is de-pressurizing the house slightly, which might exacerbate any issues I've been experiencing during less than optimal wood loads.

Stay tuned.

 

[stoveliker]

I am puzzled by the increase at the end of the active burn.
Stuff leaking out when the draft decreases (but is not zero!) is bad.
Is your CO following the VOCs?

 

[Ctwoodtick]

Ok, I’m back with some info after buying an air purifier that shows PM 2.5 levels. It was 100 dollars on amazon so I’m aware that I likely don’t have the highest precision info.
With using the purifier for about 12 hours, it seems to be picking up on very little smoke in the house. It is pretty much pegged at “006” which I am figuring is undetectable (at least for this purifier). I’ve been consciously only reloading when coals are low, so avoiding any visible smoke on reload.
For a test, I lit a candle then blew it out close up to the purifier. It quickly skyrocketed the PM to 500. For a more subtle test later, I blew out a candle that was maybe 10 feet away and the PM jumped to 80. So, it seems like it is working, at least for general reference points.
I will keep my eye on it. But that said, I am glad to see that with my current set up, I don’t appear to be impacting my indoor air too badly.
Meanwhile, I’m waiting on this southern New England snow to melt so I can get back to the pine logs that have been buried for the last 7 weeks.

 

[clancey]

DB----Now that"s a research paper. Have a nice day everyone...clancey

 

[River]

Coincidentally, I just found out that I have very early coronary artery disease.

I am not a medical professional (hence am not qualified to give medical advice), but to the best of my understanding, coronary artery disease is (more or less) clogged coronary arteries. That happens when we are insulin resistant. Insulin, although crucial for our functioning, is caustic to our cardiovascular system. In too-great doses, it damages the lining of our arteries. Our bodies' response to that is to coat the inside of the artery with cholesterol (cholesterol is not the villain we were duped into thinking it is).

Our bodies respond to high blood glucose levels by sending out insulin to:
1. facilitate the transfer of said glucose into our cells for energy,
2. signal our livers to convert glucose to glycogen and store the same in the liver, and
3. signal our livers to convert glucose to fat (which is stored in various parts of our bodies).

Carbohydrates convert easily in our digestive systems, from which they enter our bloodstreams. When we consume too many grams of carbohydrates consistently, and insulin is sent out often and in large doses, we become insulin resistant. (Consider an alcoholic or drug addict. They need greater and greater doses to achieve their goals because their bodies become resistant to the drug of their choice. The same happens with insulin.)

Although I encourage your (and all our) efforts to clean up indoor air, the solution to the conditions resulting in coronary artery disease is to stop overloading ourselves with insulin, and become insulin sensitive, again. That means a low carbohydrate diet and/or fasting.

Anyone who would like to delve into this subject more should read Dr. Jason Fung's book, The Diabetes Code. Dr. Fung is a medical professional, and can give medical advice. I recommend this book even if you are not diabetic (I am not even prediabetic, I read it and learned a lot).

 

[Ctwoodtick]

I am not a medical professional (hence am not qualified to give medical advice), but to the best of my understanding, coronary artery disease is (more or less) clogged coronary arteries. That happens when we are insulin resistant. Insulin, although crucial for our functioning, is caustic to our cardiovascular system. In too-great doses, it damages the lining of our arteries. Our bodies' response to that is to coat the inside of the artery with cholesterol (cholesterol is not the villain we were duped into thinking it is).

Our bodies respond to high blood glucose levels by sending out insulin to:
1. facilitate the transfer of said glucose into our cells for energy,
2. signal our livers to convert glucose to glycogen and store the same in the liver, and
3. signal our livers to convert glucose to fat (which is stored in various parts of our bodies).

Carbohydrates convert easily in our digestive systems, from which they enter our bloodstreams. When we consume too many grams of carbohydrates consistently, and insulin is sent out often and in large doses, we become insulin resistant. (Consider an alcoholic or drug addict. They need greater and greater doses to achieve their goals because their bodies become resistant to the drug of their choice. The same happens with insulin.)

Although I encourage your (and all our) efforts to clean up indoor air, the solution to the conditions resulting in coronary artery disease is to stop overloading ourselves with insulin, and become insulin sensitive, again. That means a low carbohydrate diet and/or fasting.

Anyone who would like to delve into this subject more should read Dr. Jason Fung's book, The Diabetes Code. Dr. Fung is a medical professional, and can give medical advice. I recommend this book even if you are not diabetic (I am not even prediabetic, I read it and learned a lot).

Thank you, I’m not diabetic myself, but have it in my family and your points about overall health are well taken. I’ll be cleaning up my diet as well as taken the med prescribed.

 

[DBoon]

I am puzzled by the increase at the end of the active burn.
Stuff leaking out when the draft decreases (but is not zero!) is bad.
Is your CO following the VOCs?

Great question about the CO levels, something I've wondered myself. My AirThings monitor doesn't monitor CO (even though it seems to monitor everything else - maybe there are regulatory requirements or legal complications for monitoring and reporting on CO). A long time ago I had a CO detector in my house that reported a numeric level (in addition to sounding an alarm) but my current detectors in this house don't report a level - they will just sound an alarm.

I do have CO detectors in my house and they've never gone off. I exhibit no signs of high CO exposure. But not a bad idea to purchase a CO detector with a numeric readout and see what it tells me.

I can understand why VOC would increase in the stove firebox at the end of the active burn, but I too am puzzled by why it seems to make its way out of the stove.

 

[bigealta]

You need a "low level" co detector for those low digital readouts. I used to have one too until it ran out of it's 10 year life span. Unfortunately the company went out of business. There are new versions and some are "Pro" versions and can be pricey.

 

[bigealta]

I'm not sure why you guys with the air issues are not doing top down starts? They save you from opening the door until a full burn cycle has gone into coaling.

Also not sure why you need to leave you door open for any amount of time at all during start up. Something is not right with that. I light my top down and immediately close the door. My draft is only just ok with a relatively short chimney.

Wet wood or sub optimal set up must be the problem?

 

[stoveliker]

The VOCs are at coaling stage so not related to fire starting mode.

 

[DBoon]

You need a "low level" co detector for those low digital readouts. I used to have one too until it ran out of it's 10 year life span. Unfortunately the company went out of business. There are new versions and some are "Pro" versions and can be pricey.

Yeah, that's a summer project to locate something and add it to my monitoring repertoire. It might tell me something important and useful.

 

[DBoon]

I'm not sure why you guys with the air issues are not doing top down starts? They save you from opening the door until a full burn cycle has gone into coaling.

I've tried top-down starts.

For cold starts, they offer no practical advantages to me.

For reloads, They are not very practical in a small firebox (I need every bit of room I can get with wood, and the coals are on the bottom to begin with). My wood is not what I would yet call optimally dry consistently, but when I get a full firebox with all optimally dry wood the firebox door is open for 5 minutes, and this is not a significant contributor to PM2.5 and not at all a contributor for VOCs. Note that I have a side-mounted loading door and that reduces smoke spillage quite a bit.

I am going to tweak my black stove pipe connection to my double-wall chimney pipe to slightly reduce the horizontal run, which should improve the draft on start ups as well.

 

[Ctwoodtick]

So a brief update. I had bought bit then returned an air purifier that had a pm2.5 read-out. It showed low levels of pm2.5 as I operated stove as normal.
I returned it and then bought a better rated air monitor (the Quingping air quality mini). This showed that the PM 2.5 levels goes up very little during normal stove operation ( including opening door to reload). Interestingly this evening, I reloaded stove and the air monitor did not register much of anything. However, my old air purifier kicked into the yellow (medium setting) for about 12 minutes or so. Maybe there was some change of air quality but not PM 2.5 or PM 10. (Which this monitor also measures).
I’m not really sure what to make of the results of this. Perhaps the pm 2.5 are not too bad. In any event, I’ll keep an eye out and see how things go. I have the purifier on and that should help can air clean in any event.
I appreciate the info you’ve all shared. Going forward I will limit number of reloads and wait for coals to burn down as much as reasonable. I had previously also been in the habit of raking the coals around while reloading so I will avoid that in the future as well. This along with my air purifier, I’m hoping will serve as good mitigation of any indoor air quality issues when using stove.

 

[DBoon]

This showed that the PM 2.5 levels goes up very little during normal stove operation ( including opening door to reload). Interestingly this evening, I reloaded stove and the air monitor did not register much of anything. However, my old air purifier kicked into the yellow (medium setting) for about 12 minutes or so.

Yes, this is what I've also found. PM2.5 might be in the 1-3 range when the stove is coaling and might get into the 10-15 range for 20-30 minutes after reload, then it drops back down and stays down in the 5 range or so during the active burn and into the 1-3 range the rest of the time. PM2.5 levels are higher for me in the summer when I have the windows open.

 

[John Lehet]

I got an Airthings 2960 and have used it for a few days. Haven’t seen any upticks in PM 2.5 or VOC when running the Progress Hybrid, but it’s shoulder season, so lots of mini splits. I know I get a funky woodsmoke-creosote smell sometimes, rarely when the stove goes black under some conditions. But not since I’ve had the instrument. I’ll keep an eye on that.

BUT I put it in the bedroom. With the door closed overnight the CO2 gets to over 1200. Two adults breathing and two tiny kittens. We keep the door closed when using the mini split, and currently to contain/introduce a pair of new kittens. We’ve got a ceiling fan we rarely use, but that might help, since CO2 pools some I guess. It’s a big bedroom with vaulted ceilings and I didn’t think I’d call it very tight. We also close the door in summer when using AC. I assume it might get even higher in that situation with less of a house-chimney effect.

Not sure how alarmed I should be.

Coffee roasting smoke is (just home roasting for us), as expected, insanely bad for both VOC and PM2.5. I’ve been wearing an N95 for the last few months, but almost all of the last 7 years or so of doing it I have not. Yikes. I do try to evacuate this part of the house after I roast and do an oyster chore or go to another part of the house. Still, that’s bad.

 

[Ctwoodtick]

I got an Airthings 2960 and have used it for a few days. Haven’t seen any upticks in PM 2.5 or VOC when running the Progress Hybrid, but it’s shoulder season, so lots of mini splits. I know I get a funky woodsmoke-creosote smell sometimes, rarely when the stove goes black under some conditions. But not since I’ve had the instrument. I’ll keep an eye on that.

BUT I put it in the bedroom. With the door closed overnight the CO2 gets to over 1200. Two adults breathing and two tiny kittens. We keep the door closed when using the mini split, and currently to contain/introduce a pair of new kittens. We’ve got a ceiling fan we rarely use, but that might help, since CO2 pools some I guess. It’s a big bedroom with vaulted ceilings and I didn’t think I’d call it very tight. We also close the door in summer when using AC. I assume it might get even higher in that situation with less of a house-chimney effect.

Not sure how alarmed I should be.

Coffee roasting smoke is (just home roasting for us), as expected, insanely bad for both VOC and PM2.5. I’ve been wearing an N95 for the last few months, but almost all of the last 7 years or so of doing it I have not. Yikes. I do try to evacuate this part of the house after I roast and do an oyster chore or go to another part of the house. Still, that’s bad.

Like the advice I was getting, I think the thing to do is minimize the risk as much as you reasonably can. After that, continue doing the thing that makes you happy ( coffee).
Burning wood has become a part of my lifestyle over the last 13 years or so and I don’t plan to give it up. That said, making sure I’m doing so as safely as I can (without having the anxiety exceed the risk from PM2.5) is a priority.

 

[John Lehet]

evacuate this part of the house after I roast and do an oyster chore or go to another part of the house. Still, that’s bad.

*Outdoor* chore, not oyster chore. Autocorrect. I just can’t wait until AI is in control of everything. Oh what a world to look forward too.

 

[Ctwoodtick]

We all just assumed that you had oyster chores, like all of us. Weird that you don’t, lol

 

[DBoon]

With the door closed overnight the CO2 gets to over 1200.

This is probably what I would worry the least about - high CO2 concentrations at this rate will just make you sleepy but will cause no harm. My office (where I spend the better part of a workday) gets to 750 to 800 ppm during the day, returning to 550 ppm when I am downstairs for dinner and then hitting 650 ppm or so overnight when I am sleeping in the next room over (door open).

I know I get a funky woodsmoke-creosote smell sometimes, rarely when the stove goes black under some conditions. But not since I’ve had the instrument. I’ll keep an eye on that.

This is when I suspect you will see a spike in VOC levels. PM2.5 seems rather well contained, regardless of the burn, but with less than ideally dry wood my VOC levels can shoot up a lot (1000 to 1200 ppb) and stay their for several hours during the charcoal part of the burn.

*Outdoor* chore, not oyster chore.

I was confused that someone in Vermont would have oyster chores, in winter, no less.