Here is my latest on "dampers".
To bring you up to speed, I've got a hand fired Russo, on which I had installed a baro damper, initially. Afterward, I added an MPD, then a thermostatically controlled power damper for the under-fire draft. This set-up worked great through the whole winter season .... the thermostat would open the under-fire power damper, when it called for heat. The baro damper would keep the stove from over-firing.
Then we get to spring. A couple of mornings I woke up and my eyes were burning, slightly.
There were no CO alarms from either of two detectors. I let the stove go out and had no problem with my eyes burning. (Side note: over the last couple of years, I have developed "sulfite sensitivity", so anything that has to do with sulfur, I have to have a close look at. I even wonder, if the stove hasn't been a "cause")
I decided, I wanted to eliminate the barometric damper, as a possible cause of my eye irritation. The problem being, the barometric damper was the device, which was keeping my stove from over-firing. What I ended up doing, after removing the baro damper, was installing an "adjustable limit switch" in the outlet hot air plenum, connected in series with the power damper circuit. Also, I adjusted the power damper to restrict the air input to allow only a reasonable burn. The purpose of the limit switch being, to close the power damper, if the hot air plenum was getting too hot.
This set-up won't help most of you, due to the fact that you don't have a power damper.
But, I want to look at the barometric damper situation. It has always been of prime importance to have good integrity in the chimney system. In my opinion, cutting a 6" hole in the stove pipe, is counter intuitive! While it might work reasonably well in the winter months, due to strong draft and high stove temps, in the spring and fall, when the stove is more at idle, and is sitting there with a load of unburned coal, is when the problems might arise. With the stove making little heat, the air can stratify and not allow for a good draft. There is no good reason to think, that none of the gases will escape through the barometric damper. If you were to hold the baro damper with the shutter closed and try to fill it with water, I think, you'd find that it leaked like a sieve. Also, if you look at a baro damper, which has been in use, you'll find it totally covered with as much ash and soot as the rest of the stove pipe. Is there any reason to believe that the gases which carried this to the shutter, would not leak into the room? Barometric dampers work well on any heating device, which more or less, are on or off, i.e. oil burner, stoker, etc..
That is just my opinion.