The purpose of kitchen hoods is to remove the heat, smoke, effluent, and other contaminants. The thermal plume from appliances absorbs the contaminants that are released during the cooking process. Room air replaces the void created by the plume. If convective heat is not removed directly above the cooking equipment, impurities will spread throughout the kitchen, leaving discoloured ceiling tiles and greasy countertops and floors. Therefore, contaminants from stationary local sources within the space should be controlled by collection and removal as close to the source as is practical.
Appliances contribute most of the heat in commercial kitchens. When appliances are installed under an effective hood, only the radiant heat contributes to the HVAC load in the space. Conversely, if the hood is not providing sufficient capture and containment, convective and latent heat are ‘spilling’ into the kitchen thereby increasing both humidity and temperature. Capture efficiency is the ability of the kitchen hood to provide sufficient capture and containment at a minimum exhaust flow rate. The remainder of this chapter discusses the evolution and development of kitchen ventilation testing and their impact on system design.