Hello,
exactly one year ago, we removed our open fire place and installed a wood burning stove (Osburn 1700, EPA certified, with secondary air tubes). Everything was done professionally at rather large cost. We have a regular forced air gas HVAC to heat our house and only run the stove in the evening for maybe 4h to get a little extra warmth sitting by the fire. We have been very much enjoying it, but I am not sure if we can justify doing it, given what I learned recently about its emissions.
The reason to exchange the fireplace for the stove was to be more environmentally friendly and produce less emissions. I follow the manufacturers’ instructions in how to operate the stove pretty much precisely. We only use dry wood which we make ourselves from our own property. I am testing moisture content of every single piece I put in the firebox. Currently, we are using black locust and ash. While locust is ranked the No 1 firewood, I found it hard to get a fire going with it, as it is super hard wood. So I am using ash at the bottom and top layer and locust in the middle. I start my fire from the top.
Starting the fire is going very smoothly, hardly any smoke in the firebox, the glass stays clean throughout the whole burn cycle. What I am wondering about is the emissions in the different stages of the fire.
Recently I bought an outdoor PM2.5 (Particular matter <2.5µm) monitor as I was curious to see what happens to the air quality around my house when I make a fire. We live relatively isolated in a more rural setting, though have some large trees around us. Yesterday we had low winds but those winds went onto the direction of my PM monitor (prevailing winds) so I could monitor the dynamics of my fire over time. The picture below shows the change of PM2.5 over time. The first peak PM2.5 emission is linked to the start up and is relatively moderate and of course expected as the chimney is cold. I have the damper open all the way, I.e. 100% oxygen gets in the box. Then, the fire starts going and big flames appear, emissions go down. About 30 minutes into the burn, I closed the damper about 50% as the STT started to hit >700F and I had really big flames. For about 1h, the stove was going well and burning clean. Then, however, emissions went rather suddenly way up. Looking at my fire inside my firebox I considered still good, with flames albeit much smaller than before. All logs charred, but not all actively burning (I had loaded up the stove with 6 logs in the beginning and 4 of those were still there). I would have thought that the stove was in the “cruising stage”, a term I am reading on this forum a lot. If I had not constantly looked at my PM2.5 monitor (as I set up my fire as an experiment), I would have thought that this was an ok, long-lasting fire. I obviously did not know at what time I should have allowed more oxygen in, to prevent this massive spike in pollution.
After I opened the damper all the way emissions returned to low (normal) for a while.
Later in the fire, I entered the “coal stage”, where I had mostly large coals left at the back of the stove and no longer big flames, but still 100% open damper. At this stage, emissions again went up, were similar to startup, not great, but not as bad as before, with unburned wood in the box and 50% dampened.
So I guess my question is, how do I keep my stove operating at lowest emissions possible without looking constantly at my outdoor PM2.5 monitor? The manual says never to open the door for reload until I enter the amber state. Then reload at least 3 pieces. One is strongly discouraged to add 1 or 2 logs at a time. The fire in the amber state (even with 100% oxygen) is much less clean that the fire in the beginning with the big bright flames on 100% oxygen. But if I wanted to keep the big bright flames, I would need to keep the damper open at all times, constantly re-load and go through a lot of wood and have a huge (maybe dangerously so) fire. Plus, opening the door all the time when there are still big flames has the risk of getting smoke in the house, which I absolutely hate.
I did read up on how the EPA measures particular emissions. It is not easy to find any information, and most of it is super technical. But this is a quite good info:
www.woodheat.org
My stove is supposed to emit 1.26g of PM/h. I certainly don’t think this would be reached at the “cruising stage”, i.e. with oxygen dampened 50% and low burn rates. Though the testing procedure does incorporate this level for its final emission rating.
I guess what I am saying here is that it seems to be a constant adjustment process, to keep that fire burning in a low pollution setting. The “cruising stage” as I thought it was defined seemed super dirty. Now I am wondering, how exactly does a fire look like in the “cruising” stage? Do all the logs in the firebox need to show bright flames?
I’d welcome any tips on how I can make my evening burn as clean as possible.
exactly one year ago, we removed our open fire place and installed a wood burning stove (Osburn 1700, EPA certified, with secondary air tubes). Everything was done professionally at rather large cost. We have a regular forced air gas HVAC to heat our house and only run the stove in the evening for maybe 4h to get a little extra warmth sitting by the fire. We have been very much enjoying it, but I am not sure if we can justify doing it, given what I learned recently about its emissions.
The reason to exchange the fireplace for the stove was to be more environmentally friendly and produce less emissions. I follow the manufacturers’ instructions in how to operate the stove pretty much precisely. We only use dry wood which we make ourselves from our own property. I am testing moisture content of every single piece I put in the firebox. Currently, we are using black locust and ash. While locust is ranked the No 1 firewood, I found it hard to get a fire going with it, as it is super hard wood. So I am using ash at the bottom and top layer and locust in the middle. I start my fire from the top.
Starting the fire is going very smoothly, hardly any smoke in the firebox, the glass stays clean throughout the whole burn cycle. What I am wondering about is the emissions in the different stages of the fire.
Recently I bought an outdoor PM2.5 (Particular matter <2.5µm) monitor as I was curious to see what happens to the air quality around my house when I make a fire. We live relatively isolated in a more rural setting, though have some large trees around us. Yesterday we had low winds but those winds went onto the direction of my PM monitor (prevailing winds) so I could monitor the dynamics of my fire over time. The picture below shows the change of PM2.5 over time. The first peak PM2.5 emission is linked to the start up and is relatively moderate and of course expected as the chimney is cold. I have the damper open all the way, I.e. 100% oxygen gets in the box. Then, the fire starts going and big flames appear, emissions go down. About 30 minutes into the burn, I closed the damper about 50% as the STT started to hit >700F and I had really big flames. For about 1h, the stove was going well and burning clean. Then, however, emissions went rather suddenly way up. Looking at my fire inside my firebox I considered still good, with flames albeit much smaller than before. All logs charred, but not all actively burning (I had loaded up the stove with 6 logs in the beginning and 4 of those were still there). I would have thought that the stove was in the “cruising stage”, a term I am reading on this forum a lot. If I had not constantly looked at my PM2.5 monitor (as I set up my fire as an experiment), I would have thought that this was an ok, long-lasting fire. I obviously did not know at what time I should have allowed more oxygen in, to prevent this massive spike in pollution.
After I opened the damper all the way emissions returned to low (normal) for a while.
Later in the fire, I entered the “coal stage”, where I had mostly large coals left at the back of the stove and no longer big flames, but still 100% open damper. At this stage, emissions again went up, were similar to startup, not great, but not as bad as before, with unburned wood in the box and 50% dampened.
So I guess my question is, how do I keep my stove operating at lowest emissions possible without looking constantly at my outdoor PM2.5 monitor? The manual says never to open the door for reload until I enter the amber state. Then reload at least 3 pieces. One is strongly discouraged to add 1 or 2 logs at a time. The fire in the amber state (even with 100% oxygen) is much less clean that the fire in the beginning with the big bright flames on 100% oxygen. But if I wanted to keep the big bright flames, I would need to keep the damper open at all times, constantly re-load and go through a lot of wood and have a huge (maybe dangerously so) fire. Plus, opening the door all the time when there are still big flames has the risk of getting smoke in the house, which I absolutely hate.
I did read up on how the EPA measures particular emissions. It is not easy to find any information, and most of it is super technical. But this is a quite good info:
A non-commercial service in support of responsible home heating with wood - How is Emissions Testing Done
The Wood Heat Organization was formed to support the public in the responsible use of wood energy in the home. We fulfill our mandate by providing reliable information, by conducting research into wood heating-related issues and by representing the public interest in discussions of policies that...
My stove is supposed to emit 1.26g of PM/h. I certainly don’t think this would be reached at the “cruising stage”, i.e. with oxygen dampened 50% and low burn rates. Though the testing procedure does incorporate this level for its final emission rating.
I guess what I am saying here is that it seems to be a constant adjustment process, to keep that fire burning in a low pollution setting. The “cruising stage” as I thought it was defined seemed super dirty. Now I am wondering, how exactly does a fire look like in the “cruising” stage? Do all the logs in the firebox need to show bright flames?
I’d welcome any tips on how I can make my evening burn as clean as possible.
