Flashes in my stove?

[emt1581]

It has only happened a handful of times within the past few years. But when it does it is pretty startling. It usually makes the griddle and humidifying pot jump. What happens is there'll be a normal burn going on and then all of a sudden there's a bright flash in the firebox and the results I've described above.

What is that? Is it a backdraft or something? Does something build up in wood to make that happen?

Thanks

-Emt1581

 

[BrowningBAR]

Backpuff.

Poor draft could be the culprit in this instance due to the mild weather. You are running a full liner or Class A all the way, right?

 

[BrowningBAR]

Give it a little more air, give it a little time, and then start cutting the air back, again.

If it get's really bad, disengage the cat (open the damper), let things swirl for a bit, close the damper/engage cat, and then cut the air down slowly in stages.

 

[Woody Stover]

I'm not sure, but I think wet wood can cause a flash-over. I remember that when I was burning wet wood on a low air setting, I'd open the door and see wet, shiny creosote coating the inside of the stove. If the stove then got hotter (or I made it burn hotter) and I opened the door, that stuff would be "steaming" or smoking, I'm not sure which. Maybe someone with more knowledge could comment on this, and if it can cause a backpuff.
I don't recall how dry the OP said his wood was in other threads...

 

[Jags]

Flash back - it occurs when unburnt volatile gasses build up in the stove due to lack of enough oxygen to promote combustion. It will get to the point where it can actually pull air (oxygen) down your chimney. Once this happens you have a mini explosion. They can actually be quite violent.

Without going into specifics - I a had a stupid moment (its happens) and I caused this to happen. I thought it was gonna blow my stove into the basement. Thank gawd for 3 screws in every joint.

More air (oxygen) will prevent this. It can also happen when you start to get very significant off gassing from a new wood load and cut the primary air back too fast. Work in stages.

 

[begreen]

Puff back happens when the wood is burning, then snuffed out, usually due to a lack of air though damp wood can do this too. What happens then is the firebox fills up with wood gas. When a spark or a flame from the fire reigniting happens it ignites the unburnt gases and you get a mini-explosion. Give the fire more air, be sure your splits aren't too large for starting a fire (or use a SuperCedar), and use dry wood and kindling to prevent this from happening.

 

[firefighterjake]

Puff back happens when the wood is burning, then snuffed out, usually due to a lack of air though damp wood can do this too. What happens then is the firebox fills up with wood gas. When a spark or a flame from the fire reigniting happens it ignites the unburnt gases and you get a mini-explosion. Give the fire more air, be sure your splits aren't too large for starting a fire (or use a SuperCedar), and use dry wood and kindling to prevent this from happening.

Very similar to what folks on the job call a backdraft . . . when the fire in a tightly-insulated room or building is suffocated from a lack of oxygen, unburned gases fill the space and when oxygen is introduced by a person opening the door, smashing a window, etc. the sudden ignition of the combustible gases results in an explosion . . .

I had my own backpuff a year ago . . . put some cardboard on some small coals to start a fire . . . forgot to open up the air control . . . fire smoldered, creating excess gas until the accumulated gas ignited.

 

[begreen]

All the same thing, puff back, backpuff, back flash flash back. I think of back draft as different though. That is more like draft reversal.

 

[Jags]

I think of back draft as different though. That is more like draft reversal.

Which is probably what is happening. That flash of oxygen has to be coming from somewhere (the flame part is already established). With a stove locked down hard enough to create this situation, I can't think of anywhere else the extra O2 would come from.

 

[begreen]

The secondary manifold is usually not locked down. I think hat's where it came from on my Castine but maybe not. The air wasn't shut down enough to completely squelch reignition. And actually, if I recall correctly I had opened up the air control full about 5 seconds prior. On the 2n1 there is a thermostatic air control, could that have done the same?

 

[Jags]

Dunno - good questions. In my minds eye, I am seeing it as an "UN-natural" addition of air that is not normally present - (I.E. Kaboom). I would think the regulated air from the normal controls and design of the stoves wouldn't allow for a kaboom. Not enough "instantaneous" oxygen introduction. I could easily be wrong, though.

 

[PapaDave]

Just had this happen a couple days ago. Hot fire, so I shut the air down.
Fire didn't stop, but slowed quite a bit. A few minutes later (I was on Hearth), I happened to begin looking at the stove. At the same time, one of the splits fell, a couple sparks flew, and the built up gas went boom. Nice little puff of smoke all around the door gasket.

 

[firefighterjake]

All the same thing, puff back, backpuff, back flash flash back. I think of back draft as different though. That is more like draft reversal.

I think it is different actually . . . just a bit similar in that a low oxygen environment seems to be the common denominator. Backdraft usually is "sparked" by the sudden introduction of oxygen whereas it seems as though a backpuff is sparked by an ignition source.

 

[begreen]

I defer to your analysis jake. You've got a lot more experience with backdrafts. Dangerous stuff when it happens on a big scale.

 

[firefighterjake]

I defer to your analysis jake. You've got a lot more experience with backdrafts. Dangerous stuff when it happens on a big scale.

Oh don't do that . . . I'm just a dumb firefighter. Maybe Steve, Magic Hat or some other guys will chime in with their opinions . . . I have been wrong many a time and sometimes right.