Most people think it takes a qualified heating technician to check their gas furnace or know how to clean a gas furnace.
Truth is there are several things a homeowner can do to check and clean their own furnace.
A furnace should be checked at the very least, once a year.
Typically just before the cold season when there will be a need for the furnace to run.
However, it is good idea to also check it once during the heating season, just in case the filter is gets dirty.
The furnace filter is probably the number one thing a homeowner can do to keep their furnace running efficient and clean.
Most filters are good for about 2-3 months, depending on the cleanliness of the air, or if there are pets.
Inspect the furnace filter every other month, and replace it when the original color of the filter media can not be seen through the grayish colored dirt and/or pet fur.
Always shut off the furnace power and gas prior to performing any work on it.
Also be prepared to re-light the pilot light if you have an older furnace with a "standing pilot".
This means the pilot light is always lit.
Newer furnaces do not have standing pilots.
They light themselves with electronics, when the thermostat calls for heat.
After the power and gas is off, remove the panels.
Typically there are (2) panels that will come off by pulling up and then out.
Sometimes they may have a few screws, or clasps that turn to release the panel.
Next locate the filter.
Sometimes it is inside the furnace or it may be located in the ductwork coming into the furnace.
Inspect the filter and change as needed.
You can purchase the same size filter from a local hardware store.
Note the airflow direction of the filter.
The outlet of the filter should point to the furnace fan.
The use a vacuum cleaner with extension to carefully clean off any dust, dirt or spider webs from the furnace.
Careful not to break and components, or pull any wires loose.
Put panels back on.
Turn power and gas back on.
Re-light pilot as needed.