If you find yourself in a smoky or hot kitchen, there are several things that could be wrong:
1. The fan isn’t working.
2. There’s not enough make-up air – the swamp cooler is not working or is running slow.
3. The fan belt has broke or is loose.
4. Your filters could be clogged or one or more of them has been removed.
5. The duct has access doors that aren’t closed.
Check the breaker switches. Make sure they’re on and power goes to the fan. In many cases, this handles the problem.
In some restaurants the fan is on a timer. Check the timer to make sure that isn’t the cause of the fan not working.
Go on the roof and check if the fan switch is on. If it isn’t on, turn it on. If the fan is running, but not pulling out any air the fan belt is broken.
If the fan is running and only pulling little air, the belt might be too loose or the motor could be going out. The duct might have openings (more about that below).
Check the fan belt. You can get a new fan belt at any auto supply store and change it yourself. depending on the size. (They will carry most sizes but not the really big or really small belts). Bring the belt with you and they will give you the correct replacement.
Or maybe your fan is just too small to handle the amount of smoke created in your kitchen. Then you need to replace it with a bigger model.
There needs to be air coming into the kitchen that can replace the air that is being pulled out by the fan. Many restaurants use swamp coolers to supply the kitchen with fresh air. If the swamp cooler is not working, or not working properly, the kitchen can get smoky or very hot. Have the swamp cooler checked and/or serviced.
Make sure your filters are washed on a regular basis. (in most cases 1 to 2 times a week is sufficient).
If you have a different type of system that replaces the air in your kitchen, have that system checked.
Longer ducts have access doors. They can be taken off to get access to clean the duct. If they are not put back on, or if they fall off because they weren’t screwed on properly, they will reduce the draft of air the fan pulls out of the kitchen, and the smoke stays in the kitchen (this is rare but possible).
It is very rare that the fan can’t pull out the smoke because the duct is clogged. This could only happen if your duct hasn’t been cleaned in a very long time Or there is an inaccessible area that is not being cleaned by your service company. Depending on your volume of cooking and the kind of grease you produce the time it takes to clog a duct will vary.