To clean a natural gas furnace, a person should turn the power and gas off, clean the outside of the furnace, vacuum the inside and then clean the blower. The air filter should be replaced, and the pilot light, flame sensor and igniter should be cleaned.
The first step is to turn off the power. This can be done by either turning the switch off, or unplugging the furnace from the wall. Next, the gas valve should be turned off. The outside of the furnace should be cleaned with a clean, absorbent rag. Next, the door should be removed to provide full access to the inside of the furnace, and a vacuum should be used to remove dust and dirt. It may be necessary to use an extension hose in large furnaces.
Next, the blower should be removed and the blades should be cleaned with a stiff bristle brush. Removing the blades may make this step easier. The air filter should be removed and inspected. If it is dirty, a replacement may be necessary. The flame sensor can be removed from its housing and cleaned with a rag, while the pilot light and igniter can be dusted by blowing on them through a straw. The furnace belts should be inspected for damage, and then replaced if necessary. After cleaning, the furnace should be reassembled, and the electricity, gas and pilot light should be restarted.