Q. How often should my chimney be swept? A. Generally every 50 to 75 burnings for a wood stove or fireplace flue. For an oil burner flue it averages every 2 to 4 years, but can be as often as every year to every 20 years depending on how well the burner operates and the condition of the flue interior. Gas burner flues may need sweeping if tile liner is deteriorating. This usually happens with age or after a more efficient burner is installed.