If You Cannot Stand the Heat, Check Your Kitchen Ventilation Systems
- Kitchen ventilation is critical to food service operations, but uses a substantial amount of energy.
- A well-maintained ventilation system can save energy, as well as increase safety and comfort.
- Balancing makeup air and proper equipment placement helps increase ventilation system performance.
Food service facilities use far more energy per square foot of building space than the typical commercial building. The kitchen ventilation system, while critical to food service operations, is a key contributor to that high energy use. These systems remove heat, smoke, grease, and carbon monoxide, as well as steam from cooking and dish washing. A poorly maintained ventilation system not only wastes energy, it reduces safety, as well as worker comfort and productivity.
Understanding how a kitchen ventilation system works is important when taking steps to increase energy efficiency and improve system performance. For handling kitchen effluents, a basic ventilation system consists of a hood or canopy, ductwork, and a fan.
The hood captures the plume of heated air (including gaseous, liquid, and solid contaminants) that rises from the cooking surface. A key component is the grease filtering system, typically based on one or more of the following technologies:
- Mesh filters—consist of layers of metal mesh, which trap grease and contaminant particles as air is drawn through. They are not effective at removing high levels of grease, and must be cleaned frequently.
- Baffle filters—separate grease from an air stream by changing air speed and direction. They are more efficient than mesh filters and can be cleaned in dishwashing machines.
- Cartridge filters—are suitable for moderate to heavy grease environments. These stainless steel filters can be cleaned in commercial kitchen dishwashers.
- Water wash—cleans the cartridges in an automatic internal washing cycle. They require a direct hot water supply and are typically costly to install.
- Continuous water mist—is a very effective grease removal system. It uses a continuous mist of cold water sprayed into the extraction system. Fats are emulsified and dropped into a collection trough.
- Ultraviolet (UV)—is a recently developed technology, which integrates UV lights into the hood. The light breaks down grease molecules into smaller compounds of carbon dioxide and water vapor and carries them out through the exhaust airflow.
The Exhaust Fan
The three types of exhaust fans typically found in commercial kitchens include the following:
- Upblast. Upblast fans are the aluminum mushroom-shaped fans commonly seen on restaurant roofs. They are designed to emit kitchen exhaust away from the roof. Direct drive is a recent innovation in which there is no drive belt to wear out. Direct-drive fans can also save energy by running at variable speeds.
- Utility sets. Due to their steel construction, these roofmounted units are capable of handling large volumes of air as well as high temperatures. They are easy to clean, helping to reduce maintenance costs and increase equipment life.
- Inline. These axial fans—rarely used in food service settings—do have some application in minimal grease environments.
Ductwork for cooking exhaust systems is typically fabricated from 16- or 18-gage stainless steel. It should be liquid tight, designed with easy access for cleaning, and routed vertically to the roof as much as possible with minimal turns.
Improving Kitchen Ventilation Efficiency
These simple steps will save energy and help maintain a safe and comfortable kitchen environment:
- Make sure the right amount of makeup air is introduced into the kitchen to compensate for the air taken out by the ventilation system. Ventilation systems work less efficiently with too much or too little makeup air. Integrate your kitchen ventilation units with the building heating, ventilating, and air -conditioning (HVAC) system, bringing in air from adjacent work or serving areas.
- Minimize makeup air velocity near the canopy or hood; it should be at no more than 75 feet per minute.
- If your kitchen has a variety of cooking appliances or a variable schedule, consider using exhaust fans that can accommodate adjustable speed controls.
- Arrange cooking appliances based on how much effluent they produce. Specify different ventilation rates accordingly. For heavy effluent producers, such as char broilers, position the appliance in the center of a hood section, rather than at the end.
- Be sure access panels are properly installed and sealed, and that all sections of ductwork are accessible for cleaning.