I agree with everything that Franco described. Just to make it simpler, what he's saying is that by maintaining a consistent draft, you have consistent combustion air coming into the stove. This makes for a nice steady heat output thru the burn period (normally 12 hours depending on heat demand). Case in point - before I installed a baro, I had a hard time managing the heat output of my furnace (basically a hand fed stove with blowers to duct work). If I closed the combustion air inlet too much it would slowly cool, which made for lower draft in the chimney, which in turn made the fire run cooler even more till it was dying. If I opened the combustion air too much, it would grow hotter which created stronger draft in the chimney which would force in more combustion air which caused the furnace to run hotter still - you can see where this is going lol.. Too many trips to the basement to control combustion air
So after installing the baro, it regulated the draft to a consistent level usually .03 -.04 and I would get a 12 hour burn that would only vary by a few degrees with no fiddling. Love that
... The baro was a huge help for me!