Propane is a petroleum-based product that is used in either liquid or vapor form. Propane can only be found in its liquid form when under extreme pressure or in temperatures below -45° Fahrenheit (-42.7° Celsius). When liquid propane reaches a temperature of -44° F (-42.2° C), it boils and turns into a vapor.
Since liquid propane is an extremely cold substance, it can also be dangerous is handled improperly. Frostbite from accidental misuse is quick and extreme. In appearance, it is odorless, colorless, and tasteless and appears much like a glass of water.
Systems use either liquid or vapor propane and the two forms are not interchangeable. Heating systems like home heaters or cooking devices burn the vapor form of propane. Storage tanks keep the fuel under pressure and therefore in liquid propane form. As the propane leaves the tank and enters a non-pressurized area under normal temperatures, it is converted to vapor. Storage tanks must always be kept upright to keep the liquid regulated as it leaves the tank, as burning it could cause dangerous fires.
One of the most interesting uses of liquid propane is within the automotive industry. Liquefied Petroleum Gas (LPG) first appeared as a vehicle fuel around 1913 and has since been used primarily in the trucking industry. As of 2009, there are no passenger vehicles produced in the United States that run on LPG, although consumers interested in running their car on this fuel can obtain converter kits for their gas or diesel fueled cars.
There are several attributes of LPG that make it appealing. It is mostly produced in the United States, which cuts down on foreign reliance for fuel. It burns cleaner than gasoline and emits less toxic substances and pollutants into the air. The cost per gallon is generally less as well.
For all of its positives, there are a few negatives to liquid propane as vehicle fuel. There have been many reports of consumers being hurt from splashes of it since it can cause frostbite in an instant. Neither the cars that run on propane nor the liquid propane to run them on is not as readily available, so those who wish to use it must hunt down suppliers and take the time to put a converter kit on their car. The fact that it is petroleum-based means that it is not a renewable source, so environmentalists argue that it is another source that will eventually run out and one that is still not completely clean.