Gas furnaces are usually lighted one of two ways, an electrical ignition or a pilot flame that stays continuously lit. Electrical ignition can usually be found on newer model furnaces while the latter is mostly found on older equipment. Both do the same job of lighting the main furnace. While the electrical ignition can be easily rest by pressing a button in the furnace, lighting the pilot flame can prove to be a little more tricky.
Turn your thermostat to a temperature that demands heat, typically 80 degrees or greater.
In the furnace, locate the pilot valve. The pilot valve is a box-shaped device that has a gas line leading to it.
On the pilot valve should be a knob reading "On," "Off" and "Pilot." Turn the knob to the "Off" setting.
After waiting three minutes for excess gas to dissipate, find the pilot coming out of the pilot valve, located near the burners.
Strike your match and hold it to the pilot while simultaneously turning the pilot knob to the "On" setting and depressing it for roughly 30 to 60 seconds, or until the pilot stays lit.
After the pilot flame is lit, the thermostat can be adjusted freely.