A. Propane (LP) gas. You have this type if your gas comes from a tank located outside close to your house. Propane gas is heavier than air, so it will sink to the floor and spread. Consequently, it is much more dangerous than natural gas, which is lighter than air and dissipates much easier. If you smell propane (LP) gas exit your home immediately. You have an emergency. Seek immediate help either from your Propane supplier or 911. If you are able, shut the propane gas supply off at the tank.
B. Natural gas. You have this type if you have a gas meter and pay a natural gas supplier or utility. Natural gas has a smell agent added to it as a warning of a leak. If you smell gas faintly, check all areas of your house for strong odor. Include the basement or crawl space and the attic in your search. If the odor is strong anywhere, exit your home immediately. You have an emergency. Call your heating contractor, the gas company, or 911. You need immediate help. You should know how to turn the gas off to your home at the meter. If the smell is only faint throughout all areas of your home, call your heating contractor to get it fixed. Keep the house ventilated by opening windows.