Posted: Aug 20, 2012
Purchasing a commercial exhaust system for a kitchen is incredibly important. Hoods are needed to vent exhaust from gas burning appliances and to vent excess heat generated by equipment, but they can also be used to vent grease exhaust, light up cooking areas, and even act as a fire failsafe. Here are the elements of a traditional exhaust system, and some of the factors to look at while shopping for them:
Ventilation Hood: The largest piece of a commercial exhaust system is the ventilation hoods. There are two varieties of exhaust hoods, both of which come in wall adjacent and island models:
- Heat Exhaust Hoods – These commercial hoods are intended to vent fumes (or smoke) and equipment that produce high levels of heat. This type of hood is ideal to vent things that cook at high temperatures such as double stack convection ovens or pizza ovens.
- Grease Exhaust Hoods – Grease Hoods vent exhaust and heat much like a heat exhaust hood does, however they feature slotted hood filters that also trap grease, exhaust and soot. These hoods are intended to be placed over griddles, deep fryers, and charbroilers.
It is important to examine the equipment that will be running in your commercial kitchen while shopping for a commercial hood, not only to be assured it will be vented properly (especially when dealing with equipment that produce greasy exhaust), but also to coincide with national, state, and local ordinances. These ordinances not only decide what pieces of equipment need to be under what variety of hood, but also required certifications (NSF, UL, ETL listings, etc.) and the necessary clearance size. It is often the case that hoods are required to extended past the end of the cooking area by a certain distance. For more information on sizing your hood system properly, check out your county’s restaurant regulations and our RESTAURANT GREASE & HEAT HOOD SIZING GUIDE.
Exhaust Fan: Every commercial hood system requires a commercial exhaust fan to properly vent a kitchen. These fans can be either mounted on the roof of a building or on a wall, depending on the layout of your kitchen. Exhaust fans vary in power, and traditionally the higher HP units are intended to vent larger kitchens or kitchens with extensive fry banks. There are models that have an upblast or downblast exhaust so they exhaust according to code and to ensure that exhaust is not directed somewhere it should not be (whether it be to avoid a hazardous situation, a make-up air fan, or a neighboring building).
Make-Up Air Fans: An exhaust fan is constantly drawing air out from a kitchen while it is running, and instances when there is little or no other air circulation, a make-up air fan will be required. A make-up air fan is mounted in the same area as an exhaust fan (usually a roof), and their primary function is to take in air to pump air back into the kitchen. Though they are placed near the exhaust fan, they must be placed in an area that ensures they will not be pumping exhaust through the make-up air channel. This air is pumped down back into the kitchen to create a steady flow of air that works to channel exhaust into the hoods and keep the air in the non-vented areas where it is intended to be. This acts as a bit of an air curtain, and can preserve energy on air-conditioning and restaurant heating.
Vents / Ducts, Curbs & Caps: Every commercial hood system will require some sort of duct work to be functional. Hoods funnel exhaust through vents, which lead to the exhaust fan and make-up air fans. They have vents that lead back into the kitchen. Both of the vents for the fan units will require a curb where the vents meet the roof / wall, and a cap. This is necessary so that the fan can be affixed directly to the vent. In addition to a normal vent, the make-up air unit will require a fire damper as it would be a fire hazard to project fresh air directly into an area being vented.
Fire Suppression Systems: It is common, and in some cases mandatory, that commercial exhaust systems be equipped with fire suppression systems. These systems lead from a tank of fire suppressing agent (such as ANSUL or other approved flame retardants) to a series of pipes that end in a series of sprinklers resting above the cooking area. These units can be activated both manually and automatically should their heat sensors be set off. Depending on the kind of equipment you have resting under your hoods, it may be necessary to get a custom high heat fire suppression system as excessive heat from certain types of equipment (such as a wood fired broiler) can trigger the heat sensors on the system. Additionally, it is a must that your tank of fire suppressant be constantly full and regularly checked by certified technicians and / or a fire inspector.
Lighting: Many exhaust hoods feature lights since it can otherwise be difficult to illuminate the cooking area underneath them. These lights must feature both a socket and a globe that meet any necessary certifications by local ordinances (UL, ETL, etc.). Additionally, the globe must be constructed from the proper materials for the temperature extremes under the hoods. Many of these sockets can double as lighting for a walk-in cooler or freezer, so it is important to ensure that the globes on your lighting are designed to stand up to the heat.