Question: Dear Sir: We are a group of first grade students at West Kearns Elementary in Salt Lake City, Utah. We are studying the uses of air and air pressure in our every day world. Would you please tell us how you use your knowledge of air and air pressure in your job? You can e-mail us at Ann.Yates@granite.k12.ut.us. Thank you for your quick and timely response. Answer: We in the fireplace business have to understand air pressure in order to troubleshoot and fix fireplaces and stoves that do not work correctly. For instance, a customer may call and tell us that the stove is putting smoke into the room- instead of up the chimney. When we visit the house, we might notice that the room is very tight (no air leaking in from the windows and doors) or that a kitchen exhaust fan is nearly which is sucking air out of the room. This creates a negative pressure and actually sucks smoke back out of the stove or fireplace. Also, we have to understand chimneys, and why smoke is sucked up them. Air is needed in the room to replace air that is used to burn the wood and go up the chimney.