Propane (LP) gas: You have this type if your gas comes from a tank located outside close to your house. Propane is stored as a liquid under pressure in tanks and cylinders. In most residential applications, propane is used as a vapor. When liquid propane changes into a gas vapor, it expands in volume. This means that even a small leak of liquid propane can result in a much larger quantity of propane vapor, which can be especially dangerous in a confined space. A chemical odorant has been added to propane to give it a distinct smell. Learn to identify this odor. Propane gas is heavier than air, so it will sink to the floor and spread. To check for the presence of propane, carefully smell all over a room, especially in low spots. If you smell propane (LP) gas: Exit your home immediately. Propane gas can ignite easily. Do not light a match, start an engine, use a cell phone, or do anything that may create a spark. From a safe area, contact your propane supplier and call 911. If you are able, shut the propane gas supply off at the tank. Stay away from your home until you've been told that it is safe to return. Natural gas: You have this type if you have a gas meter and pay a natural gas supplier or utility. A chemical odorant has been added to natural gas to give it a distinct smell. Learn to identify this odor. If you smell natural gas: Exit your home immediately. Do not light a match, start an engine, use a cell phone, or do anything that may create a spark. From a safe area, contact your gas company or call 911. If you are able, turn the gas off at the meter. Stay away from your home until you've been told that it is safe to return.