A simple propane torch that is lit with a match will produce heat but since that's not its primary purpose the torch is not an efficient heater. Some features are incorporated into a propane heater that directs the flame into a more efficient pattern for heating purposes and makes the heater more convenient to use.
Propane is a clean-burning and efficient heating fuel. It is normally a gas but is compressed into a liquid for use in heaters and grills. Commercial propane is a designation based on grades, and the fuel we call propane includes other compounds, like propylene and butane. But the majority of the overall composition is propane, a hydrocarbon with a chemical formula of three carbon atoms and eight hydrogen atoms.
Many propane heaters employ a so-called piezoelectric igniter. A material, often quartz crystal, which has the property of developing an electrical potential when pressure is applied is housed in a mechanism that allows a spring-loaded hammer to strike. This action generates a spark, igniting the propane.
Propane heaters feature some element, often porcelain, that spreads the flame out in a pattern and helps to distribute the fuel's heat.
A pilot light is a small flame that uses very little fuel and is designed to burn more or less continuously. Its purpose is to be ready to light the main burner relatively quickly rather than having to light the heater from scratch with the igniter each time.
Some means of regulating temperature is a desirable feature in a heater. An automatic thermostat is a standard way of achieving this, and some of the more sophisticated heaters may have a thermostat while others may simply have a manual flame control of high and low with a range in between.
Burning propane---or other combustible materials for that matter---in small enclosed spaces can present a carbon monoxide hazard. Carbon monoxide is a product of incomplete combustion. It is odorless, and it competes with oxygen in the blood, depriving the brain and other parts of the body of oxygen. Some propane heaters are approved for use inside a dwelling, and some are not.
In addition to a carbon monoxide hazard, propane has another characteristic that warrants caution. Since propane is heavier than air, if there's a leak, propane will sink to floor level and pool there. If there happens to be an ignition source, such as the pilot light to a water heater, there is a grave risk of a fire or explosion.