Question: I am trying to solve a problem and I can't find a solution. to my Problem: I bought a home that has a wood fireplace converted to natural gas. The house is approximately 15 years old. When we use the fireplace, the gas logs get a large amount of soot build up on them. More importantly we are finding soot residue on our TV screens and computer screens that are located up stairs of our house and the fireplace is located downstairs. I doubt the chimney has ever been cleaned, but I've been told that a gas fireplace doesn't need to be cleaned. I don't know if our air flow is pulling air in reverse direction down from our chimney or what. The fireplace works much better when the doors are left open (the flames flicker straight up as supposed to) when we close the doors the flames are angled to the back due to the amount of forced air being sucked in through the bottom. One fireplace company told me to crack a window when we are using the fireplace. Living in Minnesota where it can get to -20 to -30 below zero Answer: You are probably correct. Negative pressure is causing your house to suck a certain amount of air from the fireplace..along with some soot. But you should also look at other issues: 1. Soot on the gas logs (on vented sets) is normal..even heavy soot. Take them outside and brush or host them off (assuming they are the heavy cement logs). 2. Do you have an attached garage? Do you use candles in the home? These things can cause sooting in the house. When you run your car in the garage, the exhaust can be sucked into the home and deposited on surfaces. 3. The logs MUST be used with the damper and fireplace doors full open. Any other use is asking for trouble. It is doubtful that a chimney cleaning would help this situation. More likely, crack a window a small amount and keep the doors and damper full open. If the problem persists, make the fireplace opening a few inches lower by fixing a small sheet metal hood or deflector to the top. If none of the above works, call an HVAC expert to combat the negative pressure problem in your home. He'll install a heat recovery ventilator or other system to fix the situation.