BOOM/BANG

Not sure how "dust" accumulates inside a working electric smoker. It isn't the same particulate composition or size as smoke, and smoke particles aren't very flammable unless large quantities of unburned particles somehow accumulate. I guess I'm still leaning towards unburned volatiles released from the wood, especially since it happens rather regularly in smokers using chunks, not pellets. Just my $.02.

quote:

Originally posted by Jay1924:
Not sure how "dust" accumulates inside a working electric smoker. It isn't the same particulate composition or size as smoke, and smoke particles aren't very flammable unless large quantities of unburned particles somehow accumulate. I guess I'm still leaning towards unburned volatiles released from the wood, especially since it happens rather regularly in smokers using chunks, not pellets. Just my $.02.

Smoke is a collection of airborn solid & liquid particulates (aka. dust particles) along with gasses. When these build up they can ignite.

They are different. Woodworkers and flour millers are working with dust in the air and static discharge. Firefighters deal with backdrafts and flashovers. If you watch one of these smokers just before the big bang, You can actually see them breath. The smoke will come out, and then look like it is getting sucked back in. This is a sign of incomplete combustion in an enclosed space. This is due to oxygen starvation. If they take big enough gulp of oxygen, they bang. It is called a smoke explosion.

quote:

Originally posted by Idaho Mike:
It is called a smoke explosion.

Thank you for the clarification.

Idaho Mike, I believe your observations are correct, but I believe they don't specify exactly what is igniting during the "bang" as you describe it. The composition of the gaseous atmosphere inside the smoker depends on many variables, including temperature, wood type and amount, wood moisture, wood species, and of course the other contents (i.e., product), and the pre-existing internal condition of the smoker. The conditions for ignition of that gaseous mix are complex and the chemistry is not simple. I guess the only obvious fact is that some spontaneous combustion takes place. That fact indicates either momentary oxygen starvation, as you suggest, or possibly sudden increase of flammable elements based on conditions. It's an intriguing question. I'm just glad that no one has indicated it ever caused damage.

Jay:

I am a retired firefighter. I don't understand all of the science behind it. I just know how to recognize the signs. I don't know if you have seen the big blue silos or not. We have Harveststore here. These are oxygen limiting silos for storing grain. They are basically big Thermos bottles. Dump a load of slightly green grain in one of these and you can get spontaneous combustion. This will be a smoldering fire due to low oxygen levels. The temperatures inside the silo can get to 1500 to 2000 degrees. There have been a number of incidents where Firefighters opened the vent on top of the silo. This allows oxygen to enter the container, and you get 3 things going on at once. You get the "Big Bang" or smoke explosion. You get a "Flash over", and you now have a free burning fire. This is what takes place in a "Backdraft". We had a big steel model of grain mill that we used for demonstration purposes. Dump a spoon full of flower into mill, turn on a fan, and then hit an electric igniter, and you got "Big Bang". The oxygen is not being limited in this example, and there is no smoke or heat. This is a dust explosion.

Mike, I appreciate your insights and experience. I have seen several documentaries on grain silo fires, and have been impressed with the incredible power of the results. I know from experience that ignition does not require heat depending on the fineness of the fuel and the oxygen available. I also know that the "fuel" must be subject chemically to oxidation or nothing happens. We now know that the CS smokers are subject to a loud "bang" under certain circumstances and we can try to pin down what those circumstances are. I know I'll be paying attention to try to decipher the causes. Thanks!