Vent Adjustment

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Original poster
Jul 23, 2007
I have a 55 gallon horizontal smoker I made from a drum. I cut at 21/2 inch hole on either side and fabricated a swinging door for it. I am having trouble adjusting the heat with these air vents. Anyone have a 55 gallon smoker who could give me some advice? Thanks!!!

Welcome to the SMF the best BBQ site on the net glad to have you

Shouldn't be long & you'll get your answer. I have no experience with the 55 gal drum. I may soon look into building one myself & the answers you get may help me when & if I get the bug to start construction.
Hi John!...

I probably missed you earlier since I've been offline for almost 2 months, so I'd like to take this opportunity to say Welcome to the SMF!...
...We're glad to have you aboard.

Hopefully we'll have the problem solved for you shortly...

Now...Just a few questions to help us pinpoint what the problem might be...

1.) Is it a horizontal w/ side firebox, or simply a barrel grill type smoker?

2.) Getting too hot or staying too cold or what exactly?

3.) Where are these air vents located in respect to:
.....a.) the location of the fire grate,
.....b.) the location of the exhaust flue (smokestack)

4.) Where is the exhaust flue located on the smoker in respect to:
.....a.) the level of the food grate,
.....b.) end to end on the barrel,
.....c.) top to bottom on the barrel

5.) Is there a damper in/on the exhaust flue, and are you keeping it fully open when smoking?

Also...It would be of great help to us if you could post some pics.

This should help us know what you're dealing with there so we can get you going in short order!...

Until later...
Yes Debi, its good to have him back!
And Coley, your knowledge litterly makes my head swim! Can't you just say, if your smoker is too cold, add wood, if your smokers too hot, spray it down with water? (meant as a joke).
The Prodigal Son returns.....(READ AS).....I'm Home Mom!...What's for supper?.....

Okay...If your smoker is too cold, add wood!...If your smoker is too hot, spray it down with water!.....
.....(said jokingly!)

Seriously though.....We're still waiting for those answers John...Pics too if possible.....

Don't give up...Help is on the way!!!.....

Until later...

Good job on the smoker John!...
...Like that 'Pool Cue' handle too!...

From the New 55 Gallon Horizontal Smoker Pics, I see that the pipe you're using as
the exhaust flue (smokestack) is too small.

This would result in a choked off air flow through the smoker, hence causing
temperature control problems.

To have a proper draft (i.e. to draw properly) the exhaust flue cross-sectional
area must be at least equal to the total cross-sectional area of the air intake vents.

There is a formula available which is useful in determining the proper flue size.


Using this formula, we find that the cross-sectional area of a 2.50 inch circular air
intake vent hole is equal to 4.91 sq. in. (rounded to 2 places).

Since there are two vents of this size, we need to double this number.

4.91 x 2 = 9.82 sq. in. This is the total cross-sectional area of the air intake vents,
and is the number we need in order to determine the size exhaust flue to use.

A pipe of 3.50 in. inside diameter would have an area of 9.62 sq. in. and would be
slightly too small.

A pipe of 3.75 in. inside diameter would have an area of 11.05 sq. in. and would be
large enough, but it's not a standard size.

The best alternative would be 4.00 inch clothes dryer vent (think sheet metal)
which would have an area of 12.57 sq. in. and will have breathing room to spare.

The exhaust flue will need to be relocated to a new position also.

One possible solution is shown in the graphic I've created for you below, of course, this solution
is assuming that you're going to continue to have your heat at both ends.


The exhaust flue could also be located higher, but the general concensus is that
when it is brought in at grate level, that it helps to even out the temp throughout
the smoker.

It could also be brought in slightly under the cooking grate, as there is some merit in doing this also.

Others here at SMF need to give their opinions on this to help out here.

At any rate...I hope that this helps you to get the temp control problems worked out!...

If there are additional questions, please feel free to call on me...I'm glad to help!...

Until later...
i have my exhaust stack cut in just under my food rack. it works great. at first i had it in thru the top. didn't work so good. also i have a 4" stack. one intake about 4" too. is reader supported and as an Amazon Associate, we may earn commissions from qualifying purchases.