Gaylord Provides Kitchen Exhaust Hoods with
Fire Dampers That
Automatically Reset
After a Fire system Discharge 

There are two schools of thought when it comes to fire dampers in kitchen exhaust hoods.

The first school of thought says that fire dampers should not be not allowed because once they shut there is no longer any smoke evacuation from the kitchen exhaust hood and the only thing that matters is smoke evacuation.

The second school of thought is that the fire damper prevents the fire from migrating out of the kitchen into the duct work and potentially up on to the roof. Remember that Fire Marshall’s are always looking at worst case. Even though ducts are supposed to be cleaned regularly they often are not and this leads to high fuel loads with lots of oxygen available. The only thing missing is heat, which is just down stream from the duct. Once we get all three elements of the fire triangle in place we can have a dramatic fire. Duct shafts are helpful, but not always successful, in containing a fire with a high fuel and load and lots of oxygen. Let me describe a worst case scenario. If the fire in the kitchen is a flash fire at the cooking appliance the cooking staff may be unaware that it has moved into the duct and beyond the suppression system in the hood. This fire may then get out of the shaft or up on to the roof where it may go unnoticed for some period of time greatly increasing the damage to the structure and/or involving other parts of the building and putting more people at risk, especially in multistory occupancies

Gaylord makes hoods with and without dampers. But overall are advocates of fire dampers in for the following reasons . One, the quantity smoke that a kitchen fire creates. This amount of smoke is way beyond the capability of any kitchen exhaust fan evacuate in any short amount of time. Two, A kitchen exhaust hood is designed for the minimum amount of exhaust in order to reduce the energy consumption for heating, cooling and moving the air. In our lab we have witnessed over 800 fryer fires and hundreds of over types kitchen fires during our testing of hoods to UL710 and water spray nozzles to UL 199E. This has demonstrated to us that the above is true. In addition we believe that fire dampers in kitchen exhaust hoods can reduce the spread of the fire and potentially accelerate the activation of a suppression system by increasing the build up of heat in the hood. This will reduce the time it takes to activate the system and put out the fire before it gets larger, creating more smoke, heat and thus greater risk to the building. In addition, other systems in the building use fire and smoke dampers to contain a fire in a specific location or to prevent it from migrating to other parts of the building, why wouldn’t the same logic apply here?

Because of this Gaylord Industries developed hoods that can provide the best of both worlds. By using fire dampers that are thermostatically actuated with spring return electric motors we believe we reduce the risk of fire migrating into the duct and provide smoke evacuation when ever there is no risk to the duct. When the hoods are installed and wired per our instructions the following scenarios can occur.

1. A fire starts under the hood.
   The 250 degrees stat. senses the fire and the damper closes, the exhaust and supply fan shut off
   This rapidly builds heat in the hood, which sets off the suppression system.
   Once the temperature in the duct collar drops below 250 F the damper starts to open and the exhaust fan will come on, providing smoke evacuation. The supply fan stays off.
2. A fire starts under the hood
   The suppression system activates. But, the heat build up has exceeded 250F at the duct collar.
   The fire damper will close, exhaust fan off, supply off, all energy sources off under the hood. Once the temperature drops below 250 F at the duct collar the damper opens, exhaust fan starts and supply stays off. If the temperature never exceeds 250 F at the duct collar then the exhaust fan will stay on or be started if it is off.

Because we use an electric damper that is thermostatically activated. The damper can open and close as many times as needed, if, for any reason the temperature in the hood duct collar exceeds 250 F. This is truly the best of both worlds. Smoke evacuation when ever there is no risk of spreading fire to the duct and damper activation when ever there is risk to spreading fire to the duct work.

We at Gaylord Industries believe that this is the safest, most effective, system available today. Below is a matrix showing the damper position, fan status and fire system status for reference.