A restaurant hood system is required by both Local Building Departments and Insurance Carriers across the country. These systems are expensive, highly regulated, and very technical in nature. This blog is designed to take some of the mystery out of hood systems and provide those reading it with a better understanding of the systems and the benefits they offer. This first blog defines a type 1 commercial hood system that is typically found over restaurant cooking equipment that produces grease-laden vapor. A future blog will describe type 2 hoods that cover steam- and heat-producing equipment only.
What is a Type 1 Exhaust Hood System & What are the Component Parts Associated with it?
A type 1 kitchen hood system is composed of multiple parts. A better understanding of these systems allows a restaurant owner to better negotiate with a commercial exhaust hood installer to ensure that they are getting a complete system without unexpected costs or overruns.
Figure 1 Below Shows a Typical Hood Type 1 System:
Each of these components is listed below, because hood and fire suppression systems are generally installed by a separate installer. Each is separated by trade:
Type 1 Exhaust Hood Components Installed by Hood Installers:
- The Hood Itself
- Exhaust Fan
- Make-Up Air Fan
- Roof Curbs
- Remote Control Panel to Control Fans, HVAC, Shunt Trip Breakers, and Horn Strobes
- Temperature Sensor
- Horn Strobe or Audio-Visual Fire Alarm
- Demand Control Panel for Manual Override
- Duct Work
Type 1 Exhaust Hood Components Installed by Fire Suppression Installers:
- Fire Suppression System
- Remote Control Manual Release Station
- Class K Handheld Fire Extinguisher
Type 1 Exhaust Hood Component Parts Installed by Hood Installers and Electricians
The Hood
In the past, hoods (Figure 2) were generally built by local sheet metal contractors. However, today’s type 1 kitchen hoods are built by companies that specialize in restaurant hood manufacturing. The reason for this is because current building codes require that hoods be certified by agencies such as NSF, NFPA, UL 710, and ETL.
To better understand this, all type 1 commercial hoods are built to NFPA 96 standards and are NSF-Listed. They are also either UL or ETL Listed. Building inspectors, plan examiners, and insurance agencies will look for these certifications on hoods. In many cases, building inspectors and health departments will not approve type 1 exhaust hoods that are not certified and require them to be removed.
Exhaust Fan(s)
Exhaust Fans (Figure 3) are designed to remove grease-laden vapor, smoke, and other byproducts of cooking from the kitchen environment. These fans are sized based on the size of the type 1 kitchen hood and the type of restaurant cooking equipment under the hood. It is important to size these fan(s) accordingly to ensure that the proper amount of air is being exhausted from the kitchen.
The exhaust fans require UL 705 or 762 Listing. These listings ensure that the fans will not fail during the operation of type 1 exhaust hoods and that they can hold up to the heat of a potential fire for a specified period. While there are many exhaust fans that look like restaurant exhaust fans, these fans generally burn out over a shorter period and must be replaced.
Make-Up Air Fan(s)
As opposed to exhaust air fans, which remove air from the building, make-up air fans (Figure 4) are forms of type 1 exhaust hood ventilation that bring air into the building. While they are also either UL or ETL Listed, the requirements on these fans are not as demanding as they are not generally exposed to heat.
These fans replace air being exhausted. Without these fans, the exhaust air fans will not work properly as they will starve the kitchen for air. They also play a role in providing sufficient oxygen for the combustion of gas appliances, as well as providing a curtain of fresh air in front of the cooking equipment separating staff from the obnoxious fumes associated with the cooking process.
Roof Curbs
Roof curbs (Figures 4 and 8) are transition pieces in type 1 commercial exhaust hoods that attach to a roof and are sealed to the roof by a professional roofer. The exhaust fan and the make-up air fans each have their own curb and are attached to the curb using heavy-duty screws. The exhaust fan also has a hinge kit that attaches to the exhaust air curb so the fan can be raised for duct cleaning. The make-up air curb allows for a grease cup to be attached to catch liquid grease before it spills onto the roof.
Remote Control Panel to Control Fans, HVAC, Shunt Trip Breakers, and Horn Strobes
Today’s type 1 kitchen exhaust hoods can be ordered with remote control panels (Figure 5) that interlock the exhaust air fan(s), make-up air fan(s), HVAC Systems, Shunt Trip Breakers, and Horn Strobes. Start-up and emergency shutdowns are preprogrammed into the control panel.
These control panels are easily wired by professional electricians and are electronic, thus eliminating the many contactors and relays that require regular maintenance. The cost of these panels versus hard wiring a system is about the same with added efficiency. A unique advantage of these control panels is that they have a built-in timer which reduces the number of times a fan motor will start in each period, thus increasing the life of the fan motors.
Temperature Sensor
A temperature sensor (Figure 6) is a thermistor. It’s a simple device that sends a signal to the control panel, telling it to turn the fans on when it senses heat under the type 1 kitchen hood from the cooking equipment. They are inserted into the hood with a locking mechanism and are wired to the control panel. These devices are highly reliable and are much more efficient than the duct thermostats used in the past.
Horn Strobe or Audio-Visual Fire Alarm
A horn strobe is an audio-visual device (Figure 7) that goes off if the control panel or fire suppression system senses a fire under type 1 commercial exhaust hoods. They are not required in every application, but it is safe to check with the local fire marshal to determine when they are needed.
Demand Control Panel for Manual Override
Demand control is a means to turn the hood system on manually. They are generally part of a control panel and allow someone the option to operate the system manually.
Duct Work
Duct work (Figure 8) connects type 1 exhaust hoods to the top of the roof curbs where the exhaust air is removed from the building. There are two types of ductwork, welded carbon steel and stainless steel. Welded carbon steel is usually built in a shop and carries a minimum warranty. Stainless steel ductwork is produced by a manufacturer specializing in the production of grease ducts. Stainless steel ducts are normally round and joined together with special fire-rated epoxies. The stainless option is more expensive, but requires less labor to install and goes together quicker. Both options are required to pass a duct welding test from the local building department.
Type 1 Exhaust Hood Component Parts Installed by Fire Suppression Installers
Fire Suppression System
Fire suppression systems (Figure 9) are installed by certified installers who are trained on the brand of equipment they install. These systems consist of a control head, a bottle of fire suppressant, and nozzles that are strategically placed over each piece of cooking equipment. These nozzles are connected to the fire suppressant bottle by piping that is also installed by the installer. A series of links that are designed to break in the event of a fire will shut off all gas appliances while sending a signal to the control panel to go into fire mode locking in the exhaust fan(s) while locking out all electrical appliances under the type 1 kitchen exhaust hood, the HVAC, and the make-up air fan. During this sequence, the horn strobe will also go off, signaling a fire.
Remote Control Manual Release Station
The fire suppression installer will also install a manual pull station (Figure 10) if the fire system does not detect a fire in the equipment. It is notable that many fires start in equipment that has been pulled out from under type 1 exhaust hoods. In a situation like this, the fire suppression system will not detect the fire as it is only designed to detect fires under the hood.
Class K Handheld Fire Extinguisher
Every kitchen is required to have a Class K Handheld Extinguisher (Figure 9) in the event of a fire outside of the type 1 kitchen hood. These extinguishers are required to be certified by the fire suppression company on a regular basis. Given they are generally not available through local stores, it is recommended that these be negotiated in the price of the fire suppression system.
Given the complexity of type 1 exhaust hood systems, many municipalities require engineering and architectural drawings before installing them. If you’re only installing a hood, many municipalities will accept an engineering drawing only or an engineering drawing with a life safety plan, which is much less expensive than a full set of architectural drawings. Others will allow the installer to submit cut sheets from the manufacturer for approval. The place to start on this would be the local building department, as they will have the final say in approving a permit for this type of work.
Choosing the Right Type 1 or Type 2 Exhaust Hood System for Your Kitchen
Choosing the right exhaust hood system is important, especially considering that they’re key to maintaining a safe kitchen environment and adhering to building and fire safety codes. Consider the following to determine whether you need a type 1 or type 2 exhaust system in your kitchen:
Type 1 Kitchen Hoods: These exhaust hoods include a fire suppression system and are designed for cooking that produces grease-laden vapors, such as with restaurant fryers and commercial charbroilers.
Type 2 Exhaust Hoods: Also known as condensate hoods, these exhaust hoods are used to capture heat and steam over non-grease-producing equipment, such as ovens, commercial steam tables, coffee machines, and dishwashers.
Exhaust Rate: You’ll need to calculate your cubic feet per minute (CFM), which determines the amount of air you can exhaust. The CFM depends on smoke, grease, and heat produced by your cooking equipment, along with kitchen size and cooking surface area. For example, if you’re using a char griller or fryer, you’ll need a stronger fan/exhaust rate than you would with a flat grill.
The General CFM Calculation
Determine the volume of your kitchen (height x width x depth), then multiply by 15. Why 15? Because the fan needs to exchange air around 15 times/hour. Divide that number by 60, and you’ll get the minimum CFM for your exhaust hood.
Our next blog will continue with type 1 commercial kitchen exhaust hoods, how they’re rated, and which hood works best for your application.