• Use brushes and light cleaners on your gas furnace.Jupiterimages/Comstock/Getty Images
  
  Gas furnaces use either natural gas or propane as fuel. Gas has several advantages: It can be easily lit and produces heat quickly, is typically available on demand and produces very little exhaust when it burns. However, the contaminants that gas does produce can cause problems over time, and furnaces should be cleaned regularly to prevent future issues. If you have experience cleaning gas appliances and know how to safely turn your gas off and access your furnace, you can clean the basic parts of the furnace yourself with the right products.
  
  

Brushes

• Brushes are the staple of cleaning gas furnaces. Purchase a set of brushes designed for furnace work, with cone-like shapes you can use to reach difficult places or clean up in venting. Normal brushes work well for removing dust and grime that may be lightly caked on. When cleaning the heat exchanger, use a soft brush or a cloth to make sure that the fins are dust-free.
  
  

Detergents

• Avoid using any type of flammable cleaner on your gas furnace, since leftover residue could catch on fire. Avoid using solvents and similar cleaners derived from petroleum products. If you need to use a cleaner, stick with a mild detergent or house cleaner. If the furnace has stains you cannot remove, call in a professional.
  
  

Oil

• While you should not use oils to clean your furnace, you should use a safe, nonflammable lubricating oil to help clean any gears or oil ports that you can access. Lubricating oils not only help keep these parts clean and rust-free, but they also reduce friction so that your furnace lasts longer without needing replacement parts.
  
  

Biocides

• Biocides are cleaners that you can apply to furnace vents and leave as a light film on the inner surfaces of the vents. These cleaners are designed to kill any spores that land on them, making it difficult for mold to form any colonies in your vents. If you hire a professional to clean your furnace vents, they may apply a biocide themselves.