Kitchen Ventilation System

Ventilation is the single most important factor in the design, construction and operation of commercial kitchens. Without adequate ventilation and an ample supply of clean makeup air, no kitchen will operate efficiently. There are particular objectives which the ventilation has to achieve. The objectives include the following:

1) The general ventilation through the kitchen has to introduce sufficient clean, cool air and remove the excess hot air for the occupants to breathe adequately and remain comfortable.

 2) The general ventilation has to provide sufficient air for complete combustion at burning appliances, otherwise chronic debilitating carbon monoxide poisoning could occur.

3) The general and local ventilation has to dilute and remove products of combustion from gas and oil-fired appliances. 

4) The general and local ventilation has to dilute and remove odours, vapours and steam from the cooking processes.

  5) Local ventilation has to protect against particular hazards to health arising from some cooking fumes, such as those involving direct application of heat to the food.

6) The local ventilation has to be capable of being kept clean from fat residues to avoid loss of efficiency and fire risks.

 7) The system has to be quiet and vibration-free.

The amount of ventilation required in a particular cooking area depends on various factors:

a) The type of product being cooked

b) The structure which houses the cooking area

c) The type of equipment used and local code regulations

d) Depending on your location

e) The building heat source may also play a factor.

 

Kitchen exhaust systems help to remove grease, smoke and vapour heat from the kitchen. For this, we have to use Hood.

Types of Kitchen hood

• Basically, it is two types: back shelf or proximity hoods and canopy hoods.

Back shelf Hood:

• Back shelf or proximity hoods do not overhang the front of the equipment and are designed to be mounted behind the equipment. 
• These are best suited for low cooking surface appliances such as griddles, grills, fryers, etc. These hoods may be selected for use in applications where overhead canopies are impractical (such as a low ceiling height).
• The length of a back shelf should be a minimum of the length of the cooking equipment. Back shelf hoods should be located to provide a minimum of 18” and a maximum of 24” from the cooking surface to the filters, and the distance from the front of the hood to the front of the cooking surface should not exceed 12”.

Canopy hoods:

A Hood designed in a way that it’s inside edge overhangs or extends the equipment on all exposed sides.

Canopy hoods require larger volumes of exhaust air than the back shelf design. As a result, they are suitable for ventilating any type of cooking operation.

Canopy hoods are classified according to installation:

a) Wall-mounted canopy hood

b) Single island

c) Double island

Wall-mounted canopy hood:

• 3” gap between hood and wall it means the gap should be maintained by stove and wall is 3 “ or more than 3”.
• Three finished sides.
• Minimum overhanging requirement:
• 6” on side and 6 to 12” in front sides for full capture.

Single island:

• The stove will place in the middle.
• Four finished sides.
• Baffle filters in v configuration.
• Recommended overhang: 6 to 12” on all four sides.

Double Island canopy hood:

• Two hoods will place back to back and also two stoves will place back to back.

Schematic diagram of kitchen duct with hood:

 

Type 2 hood:

Oven Hood

Condensate hood

In this type of hood direct fan is installed in the kitchen to exhaust the vapor.

How to find Hood size:

PH= 2LH+WH-(for wall mounted)

PH= 2LH+2WH-(for SINGLE AND DOUBLE ISLAND TYPE HOOD)

LH=LS+0.8H

WH=WS+0.8H

Where, LS=Length of stove

           WS=Width of stove

           LH=Length of hood

          WH=width of hood

NOTE:

        CFM= 200*PH (Heavy cooking)

        CFM= 150*PH (medium cooking)

        CFM= 150*PH (Light  cooking)

Example:

Given length of stove,LS=1.7m

           width of stove,WS=1.5m

Suppose height of the hood=1m

For medium cooking wall mounted hood

WH=WS+0.8H

      =1.5+0.8*1=2.3m

LH=LS+0.8H

     =1.7+0.8*1=2.5m

PH= 2LH+WH

     =2*2.5+2.3=7.3m=7.3*3.28=23.94ft

CFM= 150*PH (medium cooking)

        =150*23.94=3591 CFM

Note: Fresh air always taken 80% of the exhaust CFM.

Hence Required fresh air=3591*0.8=2872.8 CFM