Blaze King 40 Smoke Smell Near Stove (No Visible Smoke) on Low Burn

I have a weird phenomenon taking place with my Blaze King 40. I'm in my third winter of heating with this stove. My wood is 3 years seasoned under cover, very dry. What I have noticed is, on warmer 30 degree to 40 degree days, after loading a full box of wood, burning aggressively until cat is very engaged, I then begin to dial back the stat in small increments until I have a very small, to no flame visible. Cat is very active, glowing orange. Looking through the glass in the door, you can see the smoke drifting around the firebox, soon to be fuel for the cat. Sitting near the stove in our recliners, suddenly, my wife and I catch a whiff of smoke smell, sometimes quite strong, sometimes faintly. This was never noticed during the first two winters heating with this stove. Chimney was brushed at beginning of the season, cat was removed and inspected and cleaned, though not really needed, after this smoke smell was noticed, and reinstalled with a brand new gasket purchased from the BK dealer. On colder days we've had where temps are 0 to 25 degrees and stove is being burned with stat set at a higher range (4-5 o'clock), we don't seem to notice this at all. Also, it seems to arise when load of wood is burning down to the point where cat temp is still in the active range, but approaching the low end. What I have done to help eliminate this problem on the warmer 30 degree + days, is only place maybe two splits (approximately 2-3 inch diameter) in on the hot coals before cat temp gets within 1/3 of the active range, and burn the stove with the stat nearly wide open or dialed back between 5 and 6 o'clock. When stat is opened more and wood is literally burning rather than smoldering, smoke smell does not seem to be noticed at all. This even happens on very clear, calm days, so it's not being triggered by heavy, moist, soggy air. Chimney has very good draw, and stove never "struggles" to burn.

I've tried to pay attention to wind direction, and have tried to consider every possible reason this could be happening. Such as, is smoke being drawn back into the house through a leaky window, though the house is very well insulated with good windows. With cat being very engaged, wouldn't seem like there should really even be "smoke" exiting the chimney as my understanding is, at that point, it is basically water vapor, not smoke. What baffles me most, we never had this during the first two years heating from start to finish with this stove. My wife wants the stove taken out due to the obvious health risk and annoying smell of smoke when this happens, but I know there has to be something more behind this. I love the stove and it's heating capability. I've become convinced, this is not a stove suited for shoulder season heating on a low burn, or to heat with on warmer days, unless using only one or two small splits and burning wide open. When heating the house with single digits outside and it is packed full and burned HOT, it's amazing! I'd be interested in any theories you may have, or even if you've experienced a similar event.

I should mention, never at any time is there visible smoke exiting the stove, or even seen in the room. It is only the smell that can be detected.

 

Have you adjusted your loading door tension yet? Door gasket has likely become compressed (normal) and your latch has some wear (normal). Might be due for a peek.

With warm, mild, humid, heavy moist conditions/temps come's low draw.
Re-thinking where your low set point is in mild weather is a real consideration.

If you are running a critter/spark arrestor screen on your cap it can cause heartache and really be nearly un-noticeable from ground level. Might be due for a peek as well. Or as an old fart once instructed me.
Shoot the screen with your BB gun from different directions to clean it
Not recommended! I prefer a Sooteater with full length bristles.

Good luck.

 

Thanks for the input, I checked the door gasket back when I noticed the problem in October, and though it was tight using the dollar bill these, I did snug it up a hair anyways. When I cleaned the chimney, I always brush off the inside of the cap, but will go give it a new look, that's a quick 15 minute process.

I'll keep you posted!

 

I agree with you, 100% on the low burn. Seems like the goal is always to shut it down for a 40 hour burn, but I've concluded it just doesn't work, at least not for me. On the warmer 35-40 degree days days, a very very small "hotter" fire two or three times a day seems best. Last night was in the mid 20's outside, so, at 11pm, I loaded a 1/4 firebox of wood and and burned with my stat set to about 4 o'clock. Woke at 7:30 to nice coals and house at 72°. I conside this setting as my "low burn" to avoid the smoke smell. Attached is a picture of my thermostat to give readers an idea of what I'm looking at as well as a picture of my burn on warmer days with only two small pieces and more of a flame.

 

So from what I read, even though you bought the new gasket from the dealer, it's probably not a genuine BK gasket. Go back to the dealer and have them order you one direct from BK, tell them to drop ship it to your house...that way it will have the return address on it (where it came from)
This was a recommendation directly from BKVP.
Sounds like BK has some VERY specific gasket specs...

 

Dang! That's a horrible business strategy where money trumps service. I will definitely do this!

 

So, what would be the likelihood that my cat could need replacement after only two full seasons of heating? It seems to go into the active range quickly and stay there throughout the burning of the full load. And, as mentioned earlier, it flows bright orange on the low burn. Would a failing cat emit this random smoke smell, or should the "smell" just go up the chimney?

 

Just checked the screen. There was some creosote, but definitely not plugged. I brushed it off really good anyways. Just a side note on the smoke smell though, it was noticeable right from the start this season with a freshly cleaned chimney and a clean screen. Early part of the season was mostly low burning fires though.

 

When did you replace the gasket?

 

I know Highbeam keeps up on these BK stove issues...

 

I find that if I "burn" with no visible flame, very low-and-slow style, I can encounter a regime where gas builds up in the firebox until it instantaneously ignites all at once, like a mini explosion. The pressure from the instantaneous light-off causes some smoke to escape around the door gasket which of course results in a smoke smell in the house.

Now my stove is a hybrid, and yours is not, right? No secondary tubes on the top of the firebox for secondary flame? So it's probably different for your stove, but I throw this out there just in case. I seek to always have some flame in the top of the box, and one reason is to prevent that sudden puff.

 

November 2025 when smell started

 

I get explosions as well if dialed way back, also why I avoid too low and slow. Mine is cat only, no tubes.

 

Thanks. I'll try to think of some things.

Most of my burn season is 30-50 degrees outside while it's raining and foggy and gross. I stuff the box full and run it on low for 24 hour cycles. That is this stove's strong point. No need for part loads. The only smoke I get is if I try to reload when the stove is currently burning a load of fuel and smoke rolls out of the loading door.

The smoke from the BK, any stove, is not just CO2 and water. It's pretty stinky even when everything is clear and right so if it's getting back into your home then you will smell it. It does smell worse when the cat is failing or stalled, almost acrid, but it always has a smell.

So the biggest issue is that this stove worked perfectly for two years and then suddenly is so bad that your wife wants it gone. Something changed.
I would ask about your chimney but since this thing worked perfectly before we can rule out a structural issue. Back to what has changed. Fuel quality, other new appliances in the house competing for draft, clogged chimney (verified clean), clogged cat (can happen fast), gasket integrity (but there are other leakpoints that smoke can get out), and of course the catalyst itself is a wear item.

Yes, it is entirely possible to need a new cat after 2 years if you burn full time. I usually get 2-3 years, 10-12 k hours, the one metal cat didn't even last two years. I dislike metal cats because of this and because of cat clogging. But I can't see how even a failed cat would cause new smells inside the house.

First thing I'd ask you to try is to not burn so "Aggressively" after cat engagement. Only long enough to get the cat meter up high and the burn obviously well established. Then set the thermostat to your desired long burn setting. If you burn too aggressively at startup the thermostat starts to close the flapper from heat and then when you turn the stat down you are actually closing the thermostat on a raging fire. Chopping the throttle which makes lots of extra smoke. Then, when you do turn it down be sure that the low setting is high enough to keep the cat meter well above the active line. The lowest burn setting is different when outdoor temps are lower.

Most of us have found that the BK suggestion of a prolonged warm up burn on high is not a good thing.

 

The one other thing I would suggest (eliminating possibilities) is to put a straight edge along the the door and body. See that all is still straight.
Shouldn't have gone wrong, but a check doesn't cost anything.

If your lowest setting at similar temps as earlier years is still the same, then the flue is likely drafting the same.

 

My BK “brand” steel cat lasted for 13 months of daily burning. I even tried a vinegar bath in that time. They suck. Ceramics have lasted for at least 20 months. I burn low and slow so my cats are doing all the work.

Here’s a photo of my load today. It’s 42 degrees out and raining off and on.

 

That's what has me so baffled, nothing has changed. Same dryer, bath exhaust fans, etc.

Now, a couple months into my third year. I'm thinking my average burn is much hotter than you are describing. We have pretty cold winters, even this year already, we've had very cold temps, even below zero several nights, with daytime temps only in the low teens. A low slow burn would never cut it during these temps. I'm almost forced to burn much hotter. Would this wear my cat out sooner. It generally runs on the BK cat stat on top of the stove up in the top 3/4 range (about 5 o'clock)?

I like how you explain this! I've been getting the new charge of wood burning good, not crazy good, but definitely going. Then, I turn the stat down about 1/8" move at a time with about five minutes between adjustments. This seems to allow the fire to stabilize between adjustments. On cold nights, I will stop my adjustments near the green mark on my stat, or one mark hotter if it's going to be a really cold night. I never dial below the green mark (picture attached). I think I am failing in the area of aggressive startups though. I will have to start dialing the stat back sooner. My cat thermostat generally comes up to temp very quick, so, I generally will close the bypass within five minutes or so of a new fire. Reloads are usually done while cat stat is still in the active range and firebox has good coal bed.

 

I just reloaded my stove and brought it up to temp, closed the bypass and started gently dialing back the stat. Within about 20 minutes, the cat stat showed very hot (6 o'clock). This happens quite often. Is the cat over-firing? I wish I knew what the actual temp was as the OEM stat doesn't show actual temps, just active. My fire is "lazy" the stove is not overly hot, but the cat is very high. Is it normal for the cat stat to nearly make a full 360 degree circle when there is only a thin lazy flame in the firebox? Cat is glowing orange and will continue this way for hours.

On a side note, tonight, with the stove burning in this state, we smell no smoke at all. Brings me back to......How the heck can this smell be coming and going!?

Tonight, outside temp is 19 degrees and dropping, very windy (30 mph+), very dry air, no snow.

 

Your cat behavior looks perfect to me. Not a dead cat.

Burning high is not overfiring the cat.
You have in fact less smoke for it to chew on them if you're burning (smoldering) low. Indeed cats get hotter when burning low.

So think.all that is behaving normally.

That leaves the smoke smell.

Have you taken apart the piping? Could it be some deposits that have run I to the seams and f the connections and that outgas (stink) into the room?