There is a lot going on inside a busy commercial kitchen: half a dozen hot stovetops cooking food to perfection, multiple people chopping and handling ingredients for any number of dishes on the menu and orders served up quickly and efficiently. Mistakes that affect the health and safety of employees and patrons alike can be made at any step, which is why standards and codes exist for nearly everything inside a commercial kitchen.
Appliances definitely have their own share of codes and regulations. Those large stove hoods humming away in the kitchen background may seem like overkill, but they have an impact on the overall environment of the kitchen itself.
No one wants to work in a smoky, hot, greasy kitchen. And no one wants to dine at a restaurant where those smoky and greasy odors overpower the smell of the food. Commercial kitchen hood code requirements ensure that the kitchen maintains its air quality and temperature, and that flammable grease is removed from the environment. This all makes the kitchen a safer place to work.
Why Are Stove Hoods Important?
Commercial stove hoods draw air up from stoves and other cooking appliances in order to reduce the level of heat, smoke and airborne grease in the kitchen. This improves air quality and safety within the kitchen. It also prevents that greasy, smoky odor from reaching your guests in the dining room.
Poor air quality can affect the respiratory system of employees who spend hours-long shifts in the kitchen, leading to health issues. Plus, no one wants the chef coughing over their food. But stove hoods do not only draw up smoke before it can diffuse throughout the kitchen. They also pull hot air up and away from the face of the cook, while keeping airborne grease away from cooking areas in order to prevent grease fires.
But not all stove hoods do a great job. That is why restaurant hood regulations exist. They ensure that a stove hood operates efficiently and maintains optimal air quality and temperature. Without such requirements, restaurants could get away with installing sub-par hoods that do not actually work.
Restaurant Vent Hood Requirements
There are two types of ventilation hoods that appear in commercial kitchens. They are aptly named Type I and Type II hoods. Type I hoods are installed over cooking appliances that produce airborne grease. Type II hoods manage non-grease vapors, such as what is produced from a dishwasher.
Therefore, when speaking in terms of stove hoods, we are referring to Type I hoods. But specific parameters can vary based on your region or municipality. The full details can be viewed in the latest copy of the International Mechanical Codes, or you can request a copy of your local mechanical codes.
Some typical restaurant vent hood requirements include:
- Must be constructed of at least 1.181 mm steel or 0.8525 mm stainless steel.
- Must be supported by non-combustible materials.
- Must extend at least 6 inches past all open edges of the stove.
- Must sit at least 18 inches above the stove.
- All exterior joints must be welded.
- Grease filters must be installed in Type I hoods at a particular height based on the type of burner.
- Grease filters must be installed with a drip tray and at a minimum angle of 45 degrees.
- Some styles of hoods are not allowed for cooktops that have excessive airflow.
Do Other Cooking Appliances Need Hoods?
So far, we have used the phrase "stove hood," which might make it seem like stoves really are the only cooking appliances that need hoods. In fact, most commercial cooking appliances need hoods, but they do not all need the same type of hood.
The type of hood needed is determined by the appliance's exhaust flow rate, calculated as cubic feet per minute (CFM), and by air temperature as it rises from the appliance. Therefore, four categories of cooking appliances exist:
- Light duty: Typically includes appliances that operate below about 400 degrees Fahrenheit, such as microwaves, electric and gas ovens, pressure cookers, cheese-melters, etc.
- Medium duty: Typically includes appliances that operate between about 400 and 600 degrees Fahrenheit, such as electric and gas fryers, ranges, pasta cookers, rotisseries, etc.
- Heavy duty: Broilers, open-flame gas ranges, etc. that typically operate between 600 and 700 degrees Fahrenheit.
- Extra heavy-duty: Any cooking appliance using solid fuel such as charcoal, wood, mesquite, etc. that exceeds 700 degrees Fahrenheit.
You will need to consult a copy of local code ordinances to find a chart that matches the type of cooking appliance with its CFM. The chart will then tell you what style of Type I commercial stove hood can handle that appliance. Hoods are not needed for certain appliances based on the amount of grease output measured at a particular CFM, typically less than 5 mg of grease per cubed mm measured at 500 CFM.
Different Styles of Type I Commercial Stove Hoods
There is no one-size-fits-all Type I commercial stove hood. There are six major types that can be grouped into two categories: canopy and close proximity (sometimes just called "proximity"). The canopy hoods rise above the cook's head, whereas the proximity hoods sit much closer to the cooking surface (but at least 18 inches away) and are never used for extra heavy-duty appliances. The specific styles include:
- Wall-mounted. This canopy hood does as it says: mounts to the wall. It can be used for extra heavy-duty appliances at 550 CFM, heavy-duty appliances at 400 CFM, medium-duty appliances at 300 CFM and light-duty appliances at 200 CFM.
- Single island. This type of canopy hood is mounted to the ceiling and hangs over a single island, where the appliances do not back up to a wall or to other appliances. It is the most powerful/versatile hood, as it can handle extra heavy-duty appliances at 700 CFM, heavy-duty appliances at 600 CFM, medium-duty appliances at 500 CFM and light-duty appliances at 400 CFM.
- Double island. Place two single kitchen islands and their appliances back to back, and you have a double island. Therefore, the double island canopy hood is twice as large as a single island canopy hood, but not necessarily twice as powerful. It is appropriate for extra heavy-duty appliances at 550 CFM, heavy-duty appliances at 400 CFM, medium-duty appliances at 300 CFM and light-duty appliances at 250 CFM.
- Pass over. This close proximity hood sits above the appliances and is suitable for heavy-duty appliances at 400 CFM, medium-duty appliances at 300 CFM and light-duty appliances at 250 CFM.
- Back shelf. This is another close proximity hood that sits at an angle along the back wall above the appliances, with side shields for efficiency. It is suitable for heavy-duty appliances at 400 CFM, medium-duty appliances at 300 CFM and light-duty appliances at 250 CFM.
- Eyebrow. The final close proximity hood is only appropriate for medium- and light-duty appliances at 250 CFM each.
Hood Installation Recommendations
Commercial kitchen hood code requirements tell you what you have to do when you install a stove hood, but there are additional recommendations for things you can do to increase the efficiency of your hood. For example, you should push appliances as close to the wall as possible or even install a steel ledge to close any gaps between the appliance and the wall. This helps direct airflow up into the hood.
Another way to direct airflow involves adding triangle-shaped side shields or panels to either end of the hood, which helps to prevent heat from "spilling over" the front edge of the hood. That spillover factor can also be remedied by using perforated grills on the front of the hood and by reducing turbulence by minimizing foot traffic in front of the appliance. You can also add adjustable sashes to the front of the cooktop to block air from spilling over the front even further.
Hood vents that exit through a wall have also been found to be more efficient than ceiling vents, so consider this in your kitchen design whenever possible. Finally, the distance between the cooking surface and the vent can be optimized based on the type of hood and the type of appliance. You do not want the vent to be so far away that hot air, grease, vapor and odor escape into the kitchen before the vent has a chance to do its job, so closer is better in many scenarios.
What Is Makeup Air and Do I Need This System?
With so much bad air exiting your commercial kitchen, you might actually not have enough good-quality air entering your kitchen to make up the difference. A mechanical makeup air system is highly recommended for commercial operations, but it can also be supplied by a gravitational system.
The makeup air pulled back into the kitchen needs to be approximately equal to the air exiting the kitchen via the hood exhaust systems. Likewise, the temperature difference between the air inside the kitchen and the air being brought into the kitchen via the makeup air system cannot exceed 10 degrees.
Other regulations outlined by the latest copy of the International Code Council's Mechanical Code define how far away the exhaust and makeup air vents should be from each other and what types of materials they should be made from. You should have sensors that allow you to determine that the outflow and intake of air are approximately equal and that the makeup air system operates whenever the exhaust system operates. This will help you easily keep records for inspections.
Understanding Restaurant Hood Regulations
Anyone who does not run a restaurant kitchen may take for granted that kitchen safety means far more than just food safety. In fact, there are numerous regulations and details to consider, and preparing a popular menu might end up being the easiest part of managing a restaurant.
Fortunately, when it comes to restaurant hood regulations, you really only need to worry about them when initially setting up your kitchen. And once you understand it all, you will not feel daunted in the future about making adjustments to increase hood efficiency or to add different types of hoods when renovating your kitchen.
However, it is always wise to consult with a commercial HVAC professional who knows restaurant vent hood requirements down to the last detail. This can help ease your mind about installing a stove hood safely. After all, they are important for fire prevention and the health of everyone in your restaurant, so do not make any half-baked efforts when it comes to Type I commercial hoods.
- Up.Codes: Section 507 Commercial Kitchen Hoods
- ICC Safe: 2018 International Mechanical Codes Section 506
- YouTube: National Restaurant Association: Optimize Exhaust Hoods
- Taylor, AZ: Commercial Kitchen Hood Worksheet / Checklist
- SlideShare: Hood Kitchen Exhaust
- Berriman USA: Commercial Kitchen Hood Design Guide