Start-up Smell

• If you haven't used your furnace in several months, when you first start it, it may smell like gas burning. This smell is normal; it is due to dust buildup on the furnace in the months since you last used it. Open your windows when you first start your furnace if it emits a burning odor, so that the odor will not remain in the house.
  
  

Normal Emissions

• Many gas heating systems emit a small amount of gas each time you use them. Thus, if you occasionally smell gas, it probably isn't a big deal. However, if you smell gas on a regular basis, you might have a serious gas leak. Call the gas company and discontinue use of the appliance until the company checks your appliance and makes sure it is safe.
  
  

Carbon Monoxide

• If you use a gas furnace, install a carbon-monoxide detector in your home as well as smoke detectors. Carbon monoxide, unlike most gases, is odorless, so you won't smell it if there's a leak. This gas is poisonous and causes flu-like symptoms as well as light-headedness. Prolonged exposure can cause you to pass out and eventually die. A carbon-monoxide detector alerts you to the presence of this gas; if your detector goes off, turn off the appliance and leave your home immediately. Contact the gas company from a safe place so it can fix the leak.
  
  

Gas in Other Areas

• It is not normal to smell gas in other areas of your house when using a gas furnace. If you smell gas elsewhere, call the gas company to inspect your home for gas leaks. Some technicians are unaware that gas furnaces emit a small amount of gas and may blame the odor on your furnace valves. Ask the technician to search for other leaks if this happens. Your furnace will not cause you to smell gas far away from it even if it has a leaky valve.