Many commercial kitchens focus only on getting the smoke out, while ignoring where the air comes back in. When the exhaust system continuously removes indoor air without stable fresh-air make-up, the kitchen develops noticeable negative pressure. Common symptoms include doors that are hard to open, high-velocity air rushing through door gaps, dining-room air conditioning being pulled into the kitchen, smoke escaping around the hood, and staff feeling stuffy and short of air. Make-up air is therefore not an accessory — it is a basic condition for the exhaust system to work.
The core of make-up air is air balance. However much air the exhaust fan removes, roughly that much fresh air must be brought in through a sensible path. In practice this is not a strict one-to-one, but is designed around whether the kitchen is enclosed, the pressure difference between dining and kitchen areas, the hood structure and the building. When make-up air is insufficient, the exhaust system steals air from doors, windows and the dining room; when make-up air is poorly placed, it can blow away the fume plume under the hood and reduce capture.
For hot kitchens, make-up air can also be combined with cooling. A water-cooled fresh air unit draws in outdoor air, cools it through evaporation, and delivers the treated fresh air to the chefs' working area or main make-up points, handling both make-up air and spot cooling. Unlike simply adding more exhaust, the focus here is to build a clear airflow path: fresh air enters from cleaner areas, moves through the occupied zone, and flows toward the hood and exhaust points, avoiding short-circuiting.
When designing a kitchen make-up air system, focus on supply volume, supply temperature, outlet position, velocity and duct resistance. Too high a velocity causes drafts and noise, and blowing directly at burners or the hood can disturb the thermal plume. Large hotels, chain restaurants and canteens usually need exhaust, make-up air, fume purification and spot cooling considered together, rather than each device running independently.
The water-cooled fresh air unit on the Xin Changfeng site is mainly used for kitchen make-up air and workshop spot cooling, and can be matched with cabinet centrifugal fans and kitchen exhaust systems. For users building or renovating a kitchen, plan the make-up air at the same time as the exhaust volume. Solving air balance first, then discussing cooling and comfort, is usually more effective than simply adding air-conditioning power. A stable commercial kitchen ventilation system should keep exhaust smooth, make-up air orderly and negative pressure controlled, while minimizing cold-air loss from the dining area.