Hoods and Accessories Buyers' Guide
Every commercial kitchen requires ventilation for the safety and comfort of customers and staff. A commercial exhaust hood is made to remove heat, smoke, grease, steam, and odor from the kitchen while also providing fire protection, but it is only part of the overall ventilation system required for a kitchen. Ductwork, fans, and make-up air systems must all work together with hoods to properly ventilate the space.
The only time that ducts and make-up air are not required is when a ventless hood is used. Ventless hoods cannot handle the load of high-volume kitchens or those with lots of cooking appliances, but they are popular in convenience stores, kiosks, airport restaurants, and other small kitchens where structural modifications are not feasible. This type of hood usually has louder fans than a vented exhaust hood, so many restaurateurs prefer a traditional kitchen ventilation system where possible.
Ventless hoods use a heavy-duty filter system, as these filters must remove enough grease, smoke, and odors to clean air and send it back into the room. Charcoal filters are usually used to help remove these pollutants from the air. The properties of the charcoal allow it to capture impurities in the air, but the filters must be changed regularly, because the filter stops working once the charcoal has absorbed as many impurities as it can hold.
Some ventless hoods have special features that allow them to operate with specific pieces of kitchen equipment or make operation and maintenance easier. If you are considering using a ventless hood for a fryer, keep in mind that most local regulatory codes require that the hood have a fire suppression system. Some ventless hoods include pressure sensors that will cut off the hood if the filters get too dirty. This can alert you to needed maintenance and help prevent fire hazards.
There are two main types of vented commercial exhaust hoods available. Type I hoods are made to handle grease and smoke, so this type always has built-in fire suppression and grease filters or baffles. Type I hoods are used over ranges, griddles, ovens, fryers, broilers, and any other kitchen equipment that may produce grease or smoke. Type II hoods are able to remove steam, vapor, heat, and odors from the kitchen, but are not made for grease or smoke. These are often used over dishwashers and steam tables, and may, if allowed by your local regulations, be used over ovens, steamers, or steam kettles that do not produce grease.1
There are several commercial vent hood styles available so you can find a hood that will work with your kitchen setup.
- Wall-mounted canopy hoods are hoods that are mounted onto the wall. This type of hood can be used with any type of cooking equipment installed against a wall.
- Single-island canopy hoods hang from the ceiling over a single line of cooking equipment.
- Double-island canopy hoods are made for use over a cooking island featuring back-to-back equipment.
- Backshelf hoods are usually wall-mounted, but freestanding models are available. These are made for use with counter-height cooking equipment and are usually positioned vertically closer to the equipment, so they are ideal for kitchens with low ceilings. This hood type has less coverage to allow for head clearance for cooks, so it is not intended for use with high-exhaust equipment, such as charbroilers.
- Eyebrow hoods are made to mount directly onto ovens or dishwashers. Many of these can be set up to operate only when needed, such as when the oven or dishwasher door is open, or at certain points during the cycle.
- Pass-over hoods are used over counter-height equipment. This type of hood is installed low over the equipment so that plates or trays of food can be passed over the top to servers.
It is very important to use a properly-sized restaurant exhaust hood in your kitchen. A hood that is too small will not be able to recover all of the exhaust your equipment produces, and a hood that is too large can drive your energy bills up by running a larger motor than necessary to clear the exhaust the kitchen produces. Because of this and other safety hazards inherent to the ventilation process, commercial ventilation systems should always be designed by professionals. However, knowing the basics can be helpful when it comes to setting up your kitchen.
The size of the commercial vent hood will be determined by the hood style and the type of equipment it is installed over. Each style has overhang requirements that dictate how far past the edge of the cooking equipment the hood must extend on each side. The island-style hoods have the largest overhang requirements due to the open-air nature of the setup. The backshelf and pass-over designs, however, have their front edges set back instead of hanging over to allow cooks head clearance and room to work.
It is also important to note the exhaust volume for the hood. The type of equipment below the restaurant exhaust hood will determine how much exhaust the hood must be able to handle. Side panels are often used between the end of a hood and the equipment below to eliminate cross-drafts and improve the effectiveness of the hood.
Commercial exhaust hoods are rarely meant for use over a single piece of equipment. To get the best use out of a hood, equipment is usually grouped together by the category that the type of equipment falls under.2
- Light-duty equipment includes ovens, steamers, and small kettles. These require hoods that can move 150 to 300 cubic feet per minute (CFM).
- Medium-duty appliances include ranges, fryers, griddles, and large kettles. This type of equipment requires hoods with a minimum exhaust flow rate of 150 to 400 CFM.
- Heavy-duty equipment, such as charbroilers and woks, requires hoods with exhaust flow rates of 200 to 600 CFM.
- Extra heavy-duty equipment is equipment that burns solid fuel, such as wood, charcoal, or briquettes. Pass-over and backshelf hoods are not recommended for use with this type of equipment, which requires a hood with the capability to move 350 or more CFM.
The CFM rating each piece of equipment requires from the hood will vary by its usage and the hood type. It is recommended that equipment types be grouped together as much as possible, with the highest-rated pieces in the center of the hood.
Cleaning and Maintenance
The ventilation system is one of the most expensive pieces of equipment in your kitchen, so it makes sense to keep it well-maintained to prevent problems and maximize its life. Most hoods use baffle filters, which can be made out of galvanized or stainless steel or aluminum. These filters are made to capture grease before it gets into the ducts or onto the roof, so they can get caked up with grease quickly if not washed regularly.
There are several ways to go about washing baffle filters. Some baffles have handles to make removing them from the hood simple, while others have hinges, allowing you to wash inside the filter easily. The easiest method for cleaning baffles is to run them through your dishwasher; if they have been maintained, this should wash away the grease easily. If you have gone too long between cleanings, you may need to scrub them or use a pressure washer. Another option is a baffle soaking tank, which allows you to soak the baffles in cleaner overnight, then rinse them off in the morning.
Even with perfectly-maintained baffles, there will eventually be some grease build-up in your ducts. Because of this, it is necessary to hire professional cleaners periodically for a thorough cleaning of your system. The frequency of these cleanings, as recommended by the National Fire Protection Association, vary by the type of foodservice operation. Any exhaust system used for solid-fuel appliances must be cleaned monthly.
Ventilation systems for high-volume kitchens - including those operating 24 hours a day, and those that do a lot of charbroiling or wok cooking - should be cleaned quarterly, and moderate-volume kitchens can be cleaned semi-annually. Low-volume kitchens such as churches, seasonal kitchens, or senior centers should have their ventilation systems cleaned yearly.3 Please note that these guidelines, while adopted by most regulatory agencies, may vary by location. Check your local regulations to be sure your cleaning schedule is in compliance with local laws.
Make-up air is an important part of any restaurant's ventilation system. The commercial vent hood pulls air out of the restaurant, so fresh air must be reintroduced inside or the building may experience negative air pressure. This can cause drafts, higher heating costs, difficulty opening or closing doors, and contaminated air due to inefficient ventilation.
Because make-up air has to be introduced to the building at the same rate that the exhaust hood is pulling air out, there will be a large amount of air coming into the building. Because of this, the point where the air enters must be determined carefully. Some hoods include systems for distributing make-up air through a perimeter supply, rear discharge, front-facing supply, or an air curtain. Some kitchens may be better served by wall-, ceiling-, or floor-mounted diffusers. Cross-drafts, hood style, kitchen set-up, and the overall HVAC system must be taken into consideration by ventilation professionals to ensure that the make-up air is being brought in at the optimal rate and location.
Design and Installation
All commercial exhaust systems should be designed and installed by professionals to ensure they can provide adequate ventilation for the appliances that will be in use. When getting a quote for a ventilation system, be sure to specify what you want included in your quote. You will need to know how much the restaurant exhaust hood, ductwork, make-up air, and installation will cost. You may also wish to ask that any special options - such as LED lighting, a self-cleaning cycle, or side panels - be priced separately, so that you can have an idea of how much each option is influencing your total price. Call 1-800-541-8683 to speak with one of KaTom's restaurant equipment specialists and get started on designing the perfect commercial ventilation system for your kitchen.
1. Commercial – Kitchen Hoods Whole Building Design Guide. Accessed September 2015.
2. Selecting and Sizing Exhaust Hoods Food Service Technology Center. Accessed September 2015.
3.Frequently Asked Questions International Kitchen Exhaust Cleaning Association. Accessed September 2015.