In another thread, I offered up a question which addressed the size of the VENT port needed for a given smoker. Which now forces me to ask this question of those who design and build smokers if they see this post: Is there a "rule of thumb" for the opening size of an exhaust vent? (I'm not building smokers, I'm just curious). This question comes from an observation of my Masterbuilt 40", propane fired smoker which has a relatively small (in my opinion) exhaust vent. That particular vent consists of 4, 3/4" wide x 3" long "slots" which are "baffled" by sliding a small plate over the opening, thus creating a way to open and close the vent damper. It has VERY little open space when slid wide open but seems to work as intended.. The air coming into the box comes from the same hole as the burner on the bottom of the smoker box and that particular hole diameter is approximately 8" in diameter. Lots of air can comes in that hole. Seems more than enough to make the smoker function as intended. Does the smoker work properly? Yes. I recently did a 10 # batch of polish sausage and a 5 # batch of breakfast pork links and both came out much better than I had anticipated being they were the first two batches of sausage I had ever made. Smoking brisket, pork shoulders, chickens, turkeys and LOTS of ribs has been my lot but sausage was a "test run" to see if the wife and I wanted to do more. (The simple answer is "yes") Pepperoni and Landjager will be next on the agenda in a few weeks). Anyone care to opine?