by Ernest Capraro

Created on: February 07, 2010   Last Updated: February 08, 2010

Propane and natural gas have a lot in common.  Both are used as fuels, are gaseous, can be stored in tanks and pumped through lines, and have similar safety hazards associated with them.  To compare how they are both similar and different, take a look at a few properties in turn.

CHEMICAL FORMULA

Propane is a simple hydrocarbon (a molecule made only of carbon and hydrogen).  It is a chain of three carbon atoms, attached by single bonds.  Three hydrogen atoms adorn each of the terminal carbon atoms, and two more are attached to the central carbon atom.  The chemical formula is commonly written as C3H8, but to show the structural connectivity, it may also be written as CH3CH2CH3. 

Natural gas is a mixture of gases, but is primarily methane.  Small amounts of ethane, propane, hydrogen sulfide, and other gases are present in the natural source, but the gas is purified before use as a fuel so that “natural gas” is usually interpreted as “methane”.  Methane is the smallest hydrocarbon, having only one carbon atom, surrounded by four hydrogen atoms.  Its chemical formula is CH4.

FLAMMABILITY

Both gases are extremely flammable.  They are fuels, and can only burn in the presence of oxygen or some other oxidizing chemical.  While properly stored in a pressurized tank, the gases cannot ignite.  If the tank is opened or leaking, the gas is then released into the air.  If that tank was stored in a closet or a room, it can then form an explosive mixture in the air, needing only a spark to set it off. 

Natural gas is lighter than air, so it fills a room easily.  Pure methane is odorless, so to make people aware of its presence, gas companies add a small amount of a sulfur compound (called a mercaptan or thiol) to give it an unpleasant stench.  The smell alerts people to its presence, and gives them the chance to exit the room carefully - and without generating any sparks by flipping switches or using anything electric.

Propane is slightly heavier than air, so while it can still fill a room, it has an additional hazard.  It can pool in low places, and flow along the ground over a distance.  If this flow reaches an ignition source, it can ignite and “flash” back to the source.  (Think of how a trail of gunpowder works, and then imagine it traveling through the air in the blink of an eye.)  If there is an explosive mixture (as in a confined

• 1
• 2
• 3
• Next Page >>