Question: We have a fireplace insert with a large door and a small vent under the door controlled with a handle. Turning the handle opens or closes the vents, but internal temperature appears to affect whether the little vent/damper stays open or closes. When starting a fire, should we leave the main door open for a while, or should we rely on the airflow from the smaller vent? The only other control is the flue. Answer: I'd do some guessing here...First, it's OK to leave the door cracked when starting the fire. Many stoves are difficult, if not impossible, to get going unless you do this. Secondly, if the internal fire temperature seems to affect the air supply, it would be my guess that there is a bimetal thermostat damper built into the stove. This opens when the fire gets lower and closes when the fire is hotter. It should work RELATIVE to where you initially set it. If you find this method of control unsuitable, you may be able to remove the thermostatic element and use manual draft control.