Many homes use natural gas or propane for heating, cooking and hot water.
Gas appliances that work well have a clear, steady blue flame. The flame may occasionally have some yellow and orange, too.
If natural gas or propane leaks, it can cause fires, explosions and serious health problems.
Gas poisoning can make people dizzy or tired, give them headaches or make it difficult to breathe.
A "rotten egg" odor is added to natural gas and propane to make gas leaks obvious, but not everyone can smell it easily.
Safe practices with natural gas and propane include:
Authorities suggest leaving the building immediately, if there is a suspected gas leak. The gas company, propane provider or fire department can be contacted from another, safer location.