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What makes propane gas heavier than air?


When using a fuel such as propane to power the appliances in your home, it’s a good idea to have an understanding of the properties and behaviors of your chosen energy source. 

While many people think that propane gas is “lighter’ than air and will dissipate into the atmosphere, propane is actually a dense fuel that is 50 percent heavier than atmospheric air at sea level. 

Why is it important to know the answer to the question, “Is propane heavier than air?” Because the answer helps you understand what to expect and how to react in the unlikely event that you experience a propane leak in the propane supply to your home or business. 

Propane density and its significance

Propane exists in two forms: liquid and gas. The propane in your tank is stored under pressure to keep it below its boiling point of -45℉, where it takes on a liquid form that requires less volume during storage. As liquid propane gas (LPG) is released into your appliances’ supply lines, the pressure lowers and the propane begins to “boil” off as a gas. This is what fuels and powers your home’s appliances and heating systems. 

The question of propane’s density matters when considering what safety precautions might be needed if you ever suspect a leak at your storage tank, within your supply lines, or if there’s a problem with an appliance. 

Because propane is heavier than air, the gas will settle to the lowest level possible. Outdoors, this generally isn’t a concern, as the gas is usually quickly diluted in the atmosphere and dissipated through wind and other environmental factors. Colder weather tends to hold the vapor together longer, while the gas quickly evaporates in warmer conditions

Indoors, however, leaked propane will settle in basements and crawl spaces. Like any other fuel source, should escaped propane gas build up in these areas and come in direct contact with a flame or other source of combustion, it could ignite and cause damage. Always be mindful of a “rotten egg” smell in low lying areas. While propane is naturally odorless, processors add the unpleasant scent as a safety measure and to alert users to any leaking gas. Additionally, while traditional carbon monoxide detectors won’t detect a gas leak, there are a number of products that constantly “sniff” and detect even the smallest leak and alert users immediately. 

How to detect a propane leak

If you suspect there’s a propane leak in your home or business, follow these safety guidelines:

  1. Extinguish all flames and sparks in the area. 
  2. Get everyone out of the area.
  3. Shut off the gas supply value on your propane tank.
  4. Report the leak to your propane supplier.
  5. Remain away from the area until your supplier can check the entire system.

Along the entire supply chain - from producer, supplier, and manufacturer of the appliances in your home - the propane industry has developed and improved safety mechanisms designed to limit the risk of danger to users. Although propane has a history of being a safe and reliable source of energy, it’s always a good idea to know as much as possible about the properties of your fuel source - as well as the safety precautions you should follow if there’s an issue.

Contact Ferrellgas for your propane needs

Understanding how propane behaves, and following the appropriate safety measures will ensure you enjoy years of safe, trouble-free use of your appliances and systems. Be sure to get in touch with one of our propane experts at your local Ferrellgas office should you have any questions.