# Cold Smoker Chimney Size



## oscar8987 (Jun 30, 2014)

Hi All,  I have a two box cold smoker.    The first box I use to supply the smoke to the larger smoking box (3.5' x 3' x 1.2'), using a 3.5" transfer pipe.    On the small (1.5' x 1.5' x 1.5')  fire box I use a 12" pellet smoker tube and have 4 individual 2" diameter inlet holes.    These can be opened or shut independently and I usually have just the one opened in front of the pellet tube opening.    Now my problem...I have a 3.5" chimney about 1.5' long and am thinking of replacing it with a 2" chimney which is a tad longer.    My question is: What is the optimum size and length when using a 2"-2.5" inlet?    I'm thinking the 3.5" doesn't allow enough drag and my pellet tube goes out.    I have tried various open vent combos on the induction, but unless there is a good breeze it goes out.    Does a too fat chimney suck as well as a smaller one and what is the optimal length?   Hopefully someone will have some good advice. Cheers Oscar


----------



## oscar8987 (Jul 13, 2014)

Hi Smokers, I posted this query about a week ago and no one has replied. As I am new to this site I thought I'd ask why it it so. Is my question too basic or silly? Did I use incorrect protocol or something of the like?   If I don't ask then I'll never know. Cheers Oscar


----------



## daveomak (Jul 14, 2014)

Oscar, morning.....   You are "overthinking" a very simple cold smoker....  air in and air out....  supply a warm smoke to start the draft....

My opinion....   The 2 boxes hooked in series is stopping the air flow...   Too much friction....  Also...  in order to have good air flow, you need to start a convection current and heat will start that....  I need to turn on the heat in my MES 30 to get a draft started....  the same applies to cold smoking boxes.....   If the air can't get warm, to have the draft going, a "cold air dam" will probably develop and stop the air flow......   If the chimney, or any chimney gets colder than the air in the smoker, the air will get more dense and stop the air flow....   Insulate the chimney, or get rid of it all together and just have holes in the top of the side walls for the exhaust...   that should put an end to the "cold air dam"......


----------



## oscar8987 (Jul 14, 2014)

Cheers Dave. Much appreciated. I'll take your advice and try to do away with the chimney stack. The reason for the separate box was to prevent the cheese melting when the breeze comes up and causes my barrel to catch fire and melt the cheese.

I have the capability to just use the one larger box without the primary fire box, but once again I'm trying to avoid flare ups with the pellet barrel as soon as the wind picks up.   Will post how i get on and thank you for your time. Regards Oscar


----------



## daveomak (Jul 14, 2014)

To stop flare ups, reduce the air inlet....   1 or 2 1" air inlets should be enough...  3-4 1" exhaust should be enough....


----------



## oscar8987 (Jul 14, 2014)

Thanks  Dave. When I built the fire box I looked at a photo of a cold smoker around the same size as mine and he had 5 x 2.5" holes across the bottom of the door. I have been using just one 2'' hole but still the barrel flares up when windy. I'll reduce it down with a cover piece over it. Cheers,


----------



## daveomak (Jul 14, 2014)

Let us know how it works....


----------



## oscar8987 (Jul 22, 2014)

Hi Dave, I've disabled the first box and have removed the chimney. It is going well at the moment, but I'll have a bit more confidence if it doesn't flare up when there's more wind about. Cheers.


----------

