If your gas furnace smells like rotten eggs, this is a serious cause for concern. Natural gas itself is naturally odorless. Because of this, gas and utility companies add a harmless chemical called mercaptan to natural gas to help us identify gas leaks. If you smell sulphur or rotten eggs in your home and have a natural gas furnace, it is possible you are experiencing a natural gas leak. If you suspect there is a natural gas leak in your home, you should: Evacuate your home immediately and leave the door open Don’t turn on any lights, use electrical switches, telephones, appliances, garage door openers, etc. Call us immediately from a neighbor’s home at Do not smoke, use lighters, or matches. Natural gas leaks are very serious and should be treated with the utmost urgency.