I was looking through the instruction pamphlet for my coal stove/heater the other day and noticed a safety precaution that I'm not sure would be applicable to other stoves as well including pellet. "Provide Air for Combustion Combustion of any type fuel requires oxygen. Be sure adequate makeup air is provided to the room where the heater is located. If necessary, a window should be opened an inch or two slightly to insure proper outside air supply and to prevent oxygen exhaustion below a safe level to support life." I understand an OAK on a pellet stove would negate an issue like this, however a stove that has no OAK should draw all air from a room and not just selectively the oxygen. If were to draw all air without replenishment, wouldn't this just create a negative pressure in the house, which in all likely hood wouldn't occur due to normal house leakage that exists? A stove exhaust is vented to the outside, so the byproducts of burning such as smoke and other gasses don't displace what is taken in from the room. If a condition like this is possible, is there a way to check for it? I'm not particularly worried myself as my house was built in the late 1800's and leaky as hell and the mice seem to know the outside "venting" holes to enter through, but just rather curious as to the precaution.