A gas furnace is a forced home air heating system which reacts when the temperature of the room falls below the programmed setting on a thermostat. When the indoor temperature falls below a certain level, the thermostat alerts the furnace which in turn combines air and fuel and the mixture gets ignited by an electronic igniter. The com busted hot gas begins to rise through the heat exchanger that is situated above the burner and it heats the air throughout the home. The remaining exhaust exits the gas furnace through the vents which leads it outside the home. The entire heating process in a gas furnace starts at its heart that is the furnace and is controlled by the thermostat. There are some furnaces which come with two or more burners where huge volumes of air are heated for distribution.
Here it must be noted that the byproducts of gas furnaces include carbon monoxide and many other harmful gases along with some amounts of unburned natural gas or propane. Hence, it is important that you are carful in case you are using a gas furnace. In fact, it is always a good idea to use high efficiency gas furnaces. This is because the high efficiency gas furnaces capture the exhaust gases and completely compress them before igniting them again in the second combustion chamber. As a result of this every bit of energy is squeezed from the unburned gases. However, besides these any other byproducts that result from the use of gas furnaces should be vented out from the homes through a flue pipe.