The primary function for a filter in a commercial hood is to prevent flames from being able to enter the exhaust ductwork. Any time that flames or sparks are permitted to enter duct work, there is a significant risk of serious fire occurring, possibly undetected. This could result in catastrophic damage to the building or persons inside.
Historically, there have been multiple types of filters available for commercial hood usage. Aluminum mesh filters, baffle filters and other types have been used to prevent the entry of flames and sparks into ductwork, and also to help keep other particles from entering the exhaust system. New requirements now indicate that the aluminum mesh filters are less safe to use, and these are not being installed on new commercial kitchen ventilation systems. All filters must now have the baffle style design.
Filters also help to cool the air passing through, which is another way that they can trap contaminant particles from the air and prevent them from entering the ducts. Air must pass through the filter to become cooled. The baffles, turns and cooling surfaces will help prevent any particles from remaining airborne by causing condensation.
The new requirements will help to prevent more restaurant kitchen fires and help to keep the commercial kitchen ventilation system cleaner and in better repair, as less residue will build up in the exhaust system.
Other types of filters that are acceptable in commercial hoods include water mist filters. These filters will quickly cool the heated air and allow condensation to capture and contain the particles that are passing through.
Baffle filters with high velocity cartridges have the largest surface area for condensation, allowing for the quickest cooling of the air flowing through. Grease particles can be readily removed from the air. With a larger surface area, the grease will be captured more closely to the exterior of the commercial hood, otherwise, it will be captured later in the ventilation system when it cools, which will make it more difficult to remove.