BY MARIE McCAIN
The Cincinnati Enquirer
Propane, used by millions of people each year in the United States for everything from back-yard barbecues to home heating, is one of the safest ways to provide heat, according to the National Fire Protection Association.
But the colorless, odorless gas is extremely flammable.
Propane is heavier than air, and its vapors can travel a significant distance to a source of ignition, and then flash back to their point of origin.
It also can accumulate in closed spaces and create an explosive hazard.
Used as a fuel, it is found in crude oil and natural gas and is a byproduct of petroleum refining, according to the Consumer's Corner Web site, www.propanegas.com.
A fossil fuel derived from the remains of plants and animals that inhabited the Earth millions of years ago, propane burns in the air at high temperatures and is used as a so-called bottled gas, a motor fuel, a low-temperature solvent and a source of propylene and ethylene.
Propane -- composed of three molecules of carbon and eight molecules of hydrogen -- reacts to temperature changes.
When temperatures rise, so does the pressure inside its container, and when temperatures drop, so does the pressure.
Because it does not have a natural odor, an artificial scent is added to warn of its presence.
Contact with liquid propane will cause tissue to freeze.
Propane was discovered in 1910 by chemist Walter Snelling. He built a still that separated gasoline into its liquid and gaseous components.
It is now used by more than 60 million people in the United States, and about 15 billion gallons of propane are consumed annually. In most workplaces it is present as a compressed gas. People working with propane should wear protective clothing and have adequate training.
In large-scale handling operations, workers should use non-sparking ventilation systems.
It differs from gasoline and fuel oil in that it is non-toxic and does not harm soil or water.