This document discusses the importance of regularly cleaning kitchen exhaust ducts and flues in restaurants to prevent fires. It notes that restaurant fires often start from cooking equipment and spread through uncleaned ductwork. Specifically, it recommends cleaning filters weekly and having the entire duct system professionally cleaned every six months to remove the buildup of oils and greases, which can ignite at just 370°C and spread fire through the concealed ducting. Regular cleaning and maintenance of exhaust fans is also important to prevent overheating from grease and fat buildup.