Master Forge vertical propane smoker + Mailbox Mod

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Original poster
Dec 29, 2021
I've been using the AMNPS with my two door (burner/chip tray area on bottom and cooking area on top) vertical propane smoker for several years now and while it's done pretty well, it's always a battle for airflow and either the tray going out or burning up too fast due to extra heat. (I would put the AMNPS above the chip tray and lid, but below the water tray, which I just put foil in as a drip tray). Enter the Mailbox Mod (after saying I would do it for years).

I have been reading a lot here about managing airflow in these smokers and people that run into trouble with the flue effect once the propane burner is going in the smoker, basically pushing air out of the mailbox/tube assembly as the exhaust. The pretty clear answer seems to be to not starve the propane burner for air (don't steal one of it's intake vents for the Mailbox Mod) and if necessary, put in a bigger exhaust smokestack at the top of the smoker. I'm left with a few options for where I put the ducting for the Mailbox Mod into the smoker so I wanted to throw these out if anyone had experience/opinions on this:
  • Duct input in the bottom door area (but not stealing either of the two existing air input/dampers)
    • Pros: Smoke can enter at or slightly above the propane burner to be drawn upwards towards the exhaust at the top (better flue mechanics?)
    • Cons: Less space to put it down here, there is a bit of a lip in between the bottom and upper cook area sections that could potentially make the flue effect to exhaust out the mailbox, and I've read mention of (somewhere here, can't find it) someone saying they felt that smoke pulled into or through a propane burner was not ideal
  • Duct input into the top cook area, as low as it can get
    • Pros: More room to put it up here, ducting is further up from the propane burner so no concerns of drawing the smoke through the burner. With the extra space I can probably also add a turn to the duct to get some more length on it (planning to mount the mailbox to the smoker)
    • Cons: Since we're higher up, we're into the "flue effect" already and as the hot air rises to exhaust, this might be a higher pressure area and more likely to want to push out through the mailbox
Appreciate any input you have! Thanks!
For a vertical gasser, I would consider using a tube (AMNTS). Location must be above the burner's elevation. I ended up putting the tube just inside the lower door, supported by the water tray rack. Will try to find or take a couple pics.
That's what I'm trying to get away from unfortunately. Mailbox Mod stuff is already ordered, just planning where to put it and hopefully avoiding having to patch a hole If I choose incorrectly!

With the AMNPS (and AMNPS - I have both), I found that to keep the pellets from not going out I had to set them over to one side near an air intake so they would stay lit. The extra heat from the propane burner coming up right near that spot and the invariability of wind blowing in that vent seemed to give me flare up issues now and then where the pellets would start flaming occasionally. I would also have an odd issue where instead of slowly burning through the maze and going to ash as it burned, the entire tray would be smoking with the pellets all a glassy black look to them, putting off a lot of darker not as pleasant smoke. The AMNTS showed a bit more promise at first, but I have had flame-up issues with it too (and it is a lot more dangerous to dump out/refill when hot). is reader supported and as an Amazon Associate, we may earn commissions from qualifying purchases.