8/28/2014 3:10 PM (PST)

Chimneys need cleaning because smokey fires deposit soot and tar on the inner walls forming a crust called creosote. If the creosote gets too thick, a fire can ignite it, starting a much bigger chimney fire that may endanger the house. Inspecting or cleaning is thus based on the number of fires, the wood burnt and the creosote deposits you can see. For example, if you have fires several times a week or more, year round, particularly with green wood, you'll want to schedule a cleaning every year. If you have a cured wood fire every month or so when it's cold an inspection every two years should be more than adequate. Lastly, if you open your flue, peer in with a flashlight, and scratch the surface you can judge for yourself. If the creosote is an 1/8th inch or less you have more time. If it's a 1/4 inch or more, you're playing with fire. :)