Here is a quick article from Chubb Agribusiness for protecting your home or business:
Winter heating season is upon us and this essential precaution could help prevent a catastrophe.
According to the Chimney Safety Institute of America, a chimney or heating vent should be cleaned once there is 1/8” of creosote and/or soot buildup inside the chimney and flue. The NFPA recommends in Standard 211 that chimneys and vents be cleaned once every year regardless of buildup. Why? A buildup of highly flammable creosote can catch fire, spreading from the chimney/vent to the house or structure. Most people prefer slow burning in a chimney or wood stove in order to wake up to a nice, toasty space. But keep in mind slow burning will produce more creosote, making it even more important to follow professional guidance in scheduling a cleaning.
Always enlist a professional chimney sweep. Professionals have the tools to not only clean the flue liner, but to also inspect for cracks or leaks that can lead to structural water damage and/or deadly carbon monoxide entering the structure.