Kitchen Ecology Unit
kitchen exhaust filtration
Kitchen exhaust systems provide a means to remove heat and contaminants (smoke, grease and aerosols) generated during cooking operations. While exhausting these items provides a better indoor environment, it can cause problems outdoors to neighboring facilities due to the associated odors and particulates emitted. The amount and type of contaminants generated from a kitchen exhaust application will depend on the cooking operations taking place inside. The contaminants include gases, vapors, aerosols, and particulates. Therefore, kitchen exhaust filtration must incorporate a wide range of filtration types and be versatile to provide an adequate solution.
Commercial kitchens typically include grease and moisture capture devices at the cooking locations. These may be in the form of hoods with baffle or other type of filters to remove the initial amount of grease particles.
The NFPA Standard 96 dictates the following inspection and as needed cleaning schedule for exhaust systems.
|Housing||• 42 +/- 4mm Rockwool insulation|
• 0.8 mm Pre-Coated External & Internal Finish
• Include side-access extruded aluminum tracks
|Filter Sections||• Electro-Static Precipitator Section|
• Pre-Filtration Section
• Fine Filtration Section
• Odor Removal Section
|Blower Section||Backward curve DIDW/SISW/Plug fan/EC fan|
Direct Exhaust: Direct exhaust refers to air exhausted directly from a kitchen area via a kitchen hood. This exhaust contains all the contaminants mentioned above at high loadings because the air is coming directly off of the cooking operation.
Many kitchen hoods are designed to capture a portion of the grease and steam, but a significant portion still remains to be removed or exhausted to the outdoors. Odour control is typically not addressed at the kitchen hood level.
Direct exhaust applications need correctly designed grease and moisture removal upstream of any odor control to ensure safety and performance of the system.
Secondary exhaust refers to air that has migrated from the kitchen exhaust system into an outdoor air intake of a neighboring facility. As the air travels from the kitchen exhaust location and mixes with ambient air, remaining grease and moisture typically “fall” out of the air stream and are no longer problematic. The odors can still be problematic to occupants of the neighboring facilities, because they do not “fall out” of the air system. Odor control is more easily accomplished in secondary exhaust than in direct exhaust applications due to the lower odor concentrations and the absence of grease and moisture. Secondary exhaust can often times be addressed by installing gas phase filtration in the affected air handling units.
- Grease and Smoke (Particulates)
The equipment removes the particulate contaminants (grease aerosols, moisture, other particulate) that are carried over into the exhaust air stream using electrostatic precipitators in combination with the appropriate stages of particulate filters. These include metal washable filters, high capacity bag filters, and high efficiency (MERV 16) pleated filters. In applications with lighter loading of particulates, solutions may solely use stages of particulate filters. In both cases, it is critical to performance and safety that proper maintenance, cleaning, and replacement are performed as required for the application.
- Odours (Gases)
Odours result from the release of volatile organic compounds during cooking operations. These volatile organic compounds are in the gas -phase; they are not removed by the particulate contaminant solutions mentioned above. The most widespread solution to remove these compounds is activated carbon applied in filtration cells such as metal cassettes or canisters. In some instances, applications have used a blend of activated carbon and other media. The filtration cells are commonly designed to achieve at least 0.1 seconds of residence time, however, the actual configuration and associated residence time will depend on the cooking operations taking place inside the kitchen.
- Exhaust of plume at the same level
The kitchen exhaust hood design provides optimum performance and energy efficiency in commercial kitchen ventilation systems by properly selecting and sizing exhaust hoods. Plume raised will be captured by the hood and removed by the suction of the exhaust fan at the same level.