NFPA 96/17A Class K Fire Protection Practice Test

Grease-laden vapors are the primary emissions a kitchen hood is designed to capture and remove. Cooking processes generate a mix of heat, steam, smoke, and airborne fats; among these, the grease-laden vapors pose the greatest fire risk because grease can ignite and cling to surfaces and ductwork. By sizing the hood and configuring it with appropriate face velocity and intake geometry, the system pulls these greasy vapors at the source and exhausts them, reducing accumulation in the cooking area and preventing flame and duct deposits.

Steam and smoke do occur during cooking, but they are not the focus of the hood sizing requirement in the same way. Steam is often managed by the overall ventilation rate and may condense without creating the same ignition hazard, while smoke is less consistent as a fire hazard concern than grease-laden vapors. Vapors from cleaning solvents can be present in some operations, but they are not the primary emissions the hood is designed to handle in typical kitchen hood design.