If you own a restaurant with a commercial kitchen, you need to think carefully about the ventilation. The exhaust fan in your kitchen takes up air and cooking fumes, and you have to replace that air through your HVAC system. If your fans remove too much air, you may end up with negative air pressure, which essentially "vacuum" seals doors shut, prevents smoke from leaving the kitchen and creates other issues.

To make sure that your commercial kitchen is supplied with enough air to make up what it is losing through your hood fans, there are several strategies you can use. Look at these ideas:

1. Ceiling diffusers

A ceiling diffuser is essentially a vent that you place on the ceiling of your commercial kitchen. The diffuser connects to a vent on your roof or to ducting that leads to a vent on your roof. Ideally, you should choose ceiling diffusers with adjustable louvres, rather than ceiling diffusers with slots. That way, you can customise the amount of air supply that your kitchen receives.

2. Displacement diffusers

Displacement diffusers work like ceiling diffusers but rather than just being a vent that fits to your ceiling, they are a triangular, semi-circular or rectangular shape. Their relatively large size allows them to supply more air than a ceiling diffusers, but they also require wall or floor space that you may want to use for other things like food storage.

3. Transfer from the dining room

To deal with the air you are losing through your exhaust fan, you don't necessarily need to buy expensive HVAC equipment or vents. You may simply need to open the doors between your dining room and your kitchen. As your dining room doesn't have exhaust fans running, it typically has more air and higher pressure than your kitchen. As a result, the air will automatically move from the relatively high pressure area (the dining room) to the lower pressure area (the kitchen). However, you may not want to rely on this method of air supply exclusively, as you probably don't want all of the kitchen odours in the dining room.

4. Integrated hood plenum

A hood plenum is an air supply channel that connects to your exhaust fan hood. You can buy fans that have plenums integrated into them, or you can retrofit a plenum onto an existing hood.

5. Professional HVAC assessment

While there are a number of devices you can add to boost air supply into your kitchen, you should consult with a commercial HVAC specialist to see what's right for your situation. These professionals can assess how much air you are removing from your kitchen based on the size of your hood fan and how often you run it. Then, they can advise you on the ventilation that's right for your situation.