Commercial kitchen grease ducts and other ventilation systems should undergo kitchen exhaust cleaning at least every two years, according to NFPA Code 96. This careful and detailed cleaning is necessary to prevent the buildup of grease, which can become a fire hazard if left unchecked. Grease duct cleaning also helps maintain the efficiency and performance of your ventilation system, ensuring that it continues to draw out smoke, fumes, and other contaminants from the kitchen.