Vent Hood Systems 101

Commercial Hoods are designed for both safety and for the functionality of your building. If it were not for the vent hood most of your establishment would be covered in remnants of air-born grease vapors.

The Balancing Act of Commercial Kitchens

The vent hood in a commercial kitchen is the key component or "heart" of the larger ventilation system. The ventilation system, as any experienced restaurateur can attest, is the most important investment you make in your commercial kitchen because it is what "balances the air" in your facility.

When a building's air is negatively unbalanced the problem is simple. The amount of air that exits the building through the vent hoods and exhaust fans is not being replaced with equal amounts of outside air causing negative pressure.

When replacement air doesn't come in, a building becomes desperate for air. It starts pulling air from any nook or opening in a building. The air is pulled from areas of your building which are not places you would want air pumped into your living space, such as drainage pipes and attics. This can cause unpleasant odors and excess dust and dirt inside the building.

Installation Manual Commercial Kitchen Vent Hood

How do I know if my ventilation system is not working properly?

A "front door check" is a simple test to determine whether or not your ventilation system is properly balancing the air in your facility. Go to the outside of your business and open the entrance door.

  • Is it easy to open the door from the outside?
  • Do you have to struggle to pull the door open?
  • Can you feel the vacuum pressure from inside pulling to keep the door closed?

If you answered yes to these questions it's time to have a professional evaluate your ventilation system. We emphasize this not only as a company that would love the opportunity to earn your business, but also as professionals in this industry who have worked with many restaurant owners and other commercial kitchen establishments throughout the years. We know the damage, headaches and revenue loss that a poor vent hood and ventilation system causes. If you have any issues let us help with the solutions. Please contact us at We can take the guess work out of the process and ensure your commercial kitchen is operating at its optimum level.

In regards to the "front door check" the problem again lies with unbalanced air. If replacement air doesn't come in then it also cannot go out the exhaust hood. Building pressure becomes too negative due to the exhaust fan sucking too hard on the inside of a restaurant. Additionally, without the flow of exhaust air the hood may not capture and contain steam and grease vapor. The range of problems and issues that arise due to unbalanced air is broad.

Other signs your oven hood system is not working and the air in your facility is not balance:

  • Smoke hovers
  • Temperature control settings must be constantly changed
  • Unpleasant outside odors are present inside the building
  • Hot and cold spots exist
  • Excessive dirt or dust is present
  • A haze in the kitchen and/or dining room
  • The kitchen or dining rooms are hotter than normal

If you are currently shopping for a vent hood system for a new facility keep in mind that the system in its entirety must be correctly fitted and calculated for your unique space and commercial kitchen needs to achieve optimum performance and energy efficiency. An incorrect system or improperly installed system will basically be a big hunk of expensive metal hanging from your ceiling. It will make a lot of noise, but it will not balance your air.

Vent hood systems have three main components:

- Exhaust fan 
- Return air fan (also known as 'makeup-air fan') 
- Vent hood

All three components must work cohesively together for optimal efficiency and effectively do the job. An Assessment of the facility is needed to determine the correct component for the system.

Commercial kitchen vent hoods must effectively manage the flow of grease and grease vapor to expel odor and air contaminants as well as remove moisture from the air. The exhaust fan creates a reverse draw of air through the hood to remove smoke, soot, steam, heat, and grease vapors away from your building. If this is not correctly established and maintained, grease accumulates throughout the kitchen, drastically increasing the risk of a kitchen fires. Without a properly functioning ventilation system, levels of humidity increase, thereby creating an environment that promotes mold and bacteria.

Vent Hoods

There are two types of hoods. Hoods that are fitted to manage grease and grease vapor are referred to as Type I. If the vent hood is purely for removing steam vapors and heat such as those caused by high temperature dishwashers, then the vent hood is referred to as Type II.

Here are three primary questions to consider before deciding on a commercial vent hood:

  1. How large will the vent hood be?
  2. How much air must the vent hood remove?
  3. How will this affect my building over all?

How Will the Vent Hood Affect My Building?

Your building contains a myriad of components that must work together in order to keep the structure safe and efficient. Installing a commercial vent hood introduces a new and unique variable to the existing arrangement. A building's existing configuration must be carefully assessed to ensure the new vent hood system is designed and installed properly.

A properly operating ventilation system may seem like magic - routing smoke and vapor to flow precisely in a directed stream to an intended location. However the "magic" is actually a science that involves physics, geometry, and engineering to achieve the most optimal air balance in a facility.

The new vent hood system must be precisely fitted so as to be "balanced". "Balancing a vent hood" means that the amount of air being removed is made up by forcing air back into the building. It is a tightly knit integration between your HVAC system and vent hood.

Type I vent hoods will typically be installed with a fresh air or make-up air device for this reason. A secondary make-up air fan system will be installed using a separate duct and connect to the fresh air device on your hood.

This duct is typically called a fresh air plenum and is installed in the front of the hood. It will often appear as a shallower box and have perforations along the surface. A common mistake people make is to assume the makeup air return acts as a wind screen to contain the smoke. This is not the case, as your vent hood exhaust is designed to remove the smoke, grease and vapors independent of a make-up air system.

If it were not for the make-up air, you HVAC would have to fight against the constant siphoning of air out of your building through the hood's exhaust fan. When an HVAC works harder it uses more energy and this means paying more for electricity. The amount of air being returned into your building should be a large percentage so that a much smaller percentage of air is made up through your HVAC fresh air intakes. It is important to note that local building codes vary and the amount of make-up air required may be different where you live. As a general rule, always check with your local building codes to make sure you are in compliance.

This is simply a basic overview of commercial vent hoods. There are many more elements that integrate into the ventilation system including the fire suppression system, duct work, electrical shunt trip wiring, pull stations and, much more. At Jean's Restaurant Supply we strive to empower our customers with knowledge; so we invite you to learn more about restaurant vent hoods and kitchen exhaust systems in our vent hood section. You will find a wealth of information about the various elements not covered in this section. Call us at 1-800-840-3610 to get consulting on any commercial vent hood system.