Unless you live in a vapor cave, or near one, stinky, sulfuric, rotten egg smell in your home could signify a gas leak. Natural gas is naturally an odorless gas. Suppliers add the distinctive odor to warn people of a possible leak. Since the late 1930s, due to a deadly explosion at a school in New London, Texas, and health risks from prolonged exposure to the carbon monoxide in natural gas, the US has been mandating the addition of the distinctive odor to any combustible gas within a distribution line.
Because of it's high combustibility, natural gas produces larger amounts of heat when smaller amounts are burned. This has brought natural gas to the forefront as an energy source for our homes.
One of the downsides to natural gas is the possibility of a leak. If there is a leak, there is a higher probability of a fire and explosion since it spreads quickly and is highly combustible. An electrical spark near a gas leak could ignite the natural gas.
If you suspect there is a leak in your home, leave immediately. Once outside, call your gas company (Vectren here in Bloomington, Indiana). Do NOT flip any switches in the house or use anything that may cause an electrical spark.
Stay safe and breathe easy!