Propane is a nontoxic, colorless, and odorless hydrocarbon gas, also known as liquefied petroleum gas (LPG). When stored in a pressurized tank, propane exists as a liquid and as the pressure is released, it vaporizes and turns into a gas that is used in combustion engines. Currently propane comprises roughly 2% of the energy consumed in the U.S., of which less than 2% is used for transportation fuel. The primary uses of propane are home and water heating, food refrigeration and cooking, and the powering of agricultural and industrial equipment. However, propane was designated as an alternative transportation fuel under the Energy Policy Act of 1992 and is currently the most widely used alternative fuel for transportation and the third most used fuel behind gasoline and diesel.
 

 
National Propane Gas Association
 
Propane Education & Research Council
 
Propane - Exceptional Energy