Make up air refers the air that must be introduced into the kitchen to replace air that is being removed by the CKV exhaust system.
Make up air balances the air pressure
Restaurant kitchen exhaust systems are often very powerful, removing thousands of cubic feet of air per minute. When this air is removed from the kitchen, it needs to be replaced with fresh air. Without this replacement air, you can wind up with all sorts of unpleasant and even dangerous conditions like negative air pressure, poor temperature control, back drafting and air quality problems. Also, these issues may negatively impact your energy usage. The problem can be compounded in newer buildings constructed to be airtight, which prevents the natural flow of outside air into the kitchen space. To avoid these issues a make up air unit will usually be installed on the roof (if available) or in a mechanical room, and provide a steady stream of outside make up air or tempered make up air into your kitchen.
The current codes generally mandate that the exhaust system create no more than a .02 inch water column negative pressure in the kitchen.
