My Furnace Smells Like Rotten Eggs

Mercaptan

• Natural gas and bottled gas are odorless gases, consisting mostly of methane. Gas companies add odorants, including a mixture of tertiary butyl mercaptan, dimethyl sulfide and n-hexane, to the gas to give it a recognizable smell that will help people identify a gas leak. This mixture of gases, which is usually just referred to as mercaptan, smells like rotten eggs.

Safety

• If you smell rotten eggs coming from your furnace, vacate your house immediately but leave the door open. Don’t use anything that might create a spark, including matches, lighters, light switches, phones, flashlights or any electrical equipment. Natural gas is very explosive, and even a tiny spark can ignite it. Don’t try to find the gas leak yourself. Don’t shut off any gas valves or appliances. If the gas ignites, don’t try to put it out. Let it burn. Burning gas won’t explode. Call your gas company and/or the fire department from a neighbor’s phone, and don’t go back into your house until the problem is fixed and your gas company or emergency responders tell you that it’s safe to re-enter.

Signs

• In addition to smelling rotten eggs, you might hear a hissing or a blowing sound. There might be flames, if the gas has ignited. You could also see bubbling in a wet area, or, if the leak is coming from pipelines located outside, you might see dirt blowing from a hole in the ground. There can also be dead vegetation outside, near the source of the leak.

Prevention

• Prevent gas leaks by having your furnace installed professionally. Incorrect installation can cause a slow leak that isn’t easily detected. Check the pilot light. When it’s burning properly, it emits a steady, blue flame. Follow manufacturer instructions for the proper care of your furnace. Have your furnace, vents, flues, chimney and gas lines inspected by a professional every year or two.

CSST

• Corrugated stainless steel tubing is a flexible tube that can be used to pipe natural gas into your home, if you’ve installed a new furnace. It’s usually routed underneath or through floor joists in the basement but, if it’s not properly bonded and grounded, it can cause a gas leak or fire if your house is struck by lightning. Have a licensed electrician check your CSST to verify that it’s been correctly bonded and grounded. CSST is usually coated in yellow or black and, unlike flexible connectors, doesn’t attach directly to your furnace from a floor or wall shut-off valve.