From the years 2007 to 2011, the leading cause of commercial building fires was cooking, according to the U.S. Fire Administration. With an average loss of almost $50 million in a five-year period, questions on risk and cost mitigation arose, as well as adding in a higher quality commercial hood vent.
This brought to attention the use of high-quality commercial kitchen hoods and fire suppression systems as a means to improve fire safety. Fire mitigation strategies include looking at the heat/grease system, from the cooking equipment to the commercial hood vent.
It also brought to mind the importance of moving a commercial kitchen ventilation (CKV) system out of the food-service section and into the mechanical section so engineers can design it for optimal fire safety.
Six Design Practices of Above-Ceiling Commercial Kitchen Ventilation Systems
Grease Ducts should be Designed Short, Straight, and Vertical
The idea is to provide the shortest path for smoke and heat to travel and exit outside the building. This prevents grease from becoming a potential fuel source for a fire which is usually the case when it travels through long ducts.
It is also critical that horizontal ducts are only used when necessary. A horizontal design easily involves at least two 90-degree turns that increase the potential for grease collection and additional resistance.
Obstructions such as Filters and Dampers should be Eliminated
Obstructions in the duct make it more difficult to remove potentially dangerous heat and smoke from the building. Although a CKV is likened to an HVAC system, coils, dampers, filters, and 90-degree turns have no place in a commercial hood vent.
This calls for a practical aerodynamic design for grease ducts. A hood fire suppression system is also more effective with short ducts with no multiple turns.
Use Listed Grease Ducts
Listed commercial duct products are factory-built systems that are designed with double-wall construction, resulting in stronger and more durable ducts.
The products are also manufactured with stainless steel which is more resistant to higher temperatures. In the event that a fire occurs, the grease duct won’t fail easily and add more fuel to the fire. Stainless steel is also long-lasting and durable.
Most importantly, listed ducts are factory-built which eliminates the need for on-site welding. This also eliminates missed holes and gaps caused by low-quality welding work.
Specify Design Redundancy in the Kitchen Ventilation System
If there are two hood vents, for example, one commercial hood vent can fail and kitchen operations would still continue. The same is true when there are two kitchen exhaust fans, two belts or motors, and two of every vital component.
With a redundant kitchen ventilation system, major damage can be controlled if and when it happens. It will also give kitchen staff enough time to escape, and call the fire department.
Use Listed Direct-Drive Exhaust Fans
The weakest link of a kitchen ventilation system is the fan belt that is instantaneously accelerated at startup. It is severely stressed and stretched every day, making it prone to breaking, cracking, and stretching. As it is relatively cheap, it will break at some point. Before that happens, however, it will become loose first.
To eliminate the problem caused by a loose or broken fan belt, use direct-drive exhaust fans and variable-frequency drives instead. These offer a more reliable system.
Use a Listed Demand Control Kitchen Ventilation System (DCKV)
An existing CKV system can be designed with DCKV capability with little to no cost. This will allow customers to gain more utility than from fixed speed on direct-drive fans or auto-start systems.
A well-engineered DCKV can be made with fire-prevention features such as an audible alarm that will be triggered when exhaust air temperature rises within 100°F (38°C).