i'm thinking on a 25" dia 150 gal propane tank for my SFB bullet smoker with a 48" cooking chamber with a 18" fire box....in the calc it says for a 441.56 cu inch exhaust chimney volume, for a 6" round stack it needs to be 15.63" long....i'm looking at a 6" circle and no way is there 441 cu inches there, is it talking the whole 15,63" length of exhaust stack volume holds 441 cu inches of smoke.............bob
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