Exhaust Hoods

Sizing exhaust hoods - air volume flow and capture velocities - online exhaust hood calculator

Exhaust hoods are essential in kitchens, laboratories and many industrial application for removing

• fumes
• mists
• vapors
• aerosols
• particulates
• hazardous substances
• polluting contaminants

In general, for an exhaust hood to be efficient

• the height - y - should not exceed 1.20 m (4 ft)
• the distance - x - should not be less than 1/3 y
• the capture velocity - v₁ - should not be less than 0.15 - 0.20 m/s (30 - 40 ft/min)

Note! Potential hazardous and polluting applications requires special solutions. Always check local regulations.

The capture velocity - v₁ - of the exhaust hood can be estimated with the empirical equation

v₁ = q / 2 y² c (1)

where

v₁ = capture velocity (m/s)

q = air volume flow (m³/s)

y = distance between table and exhaust hood (m)

c = circumference of the hood (m)

(1) can be modified to calculate required air volume

q = 2 v₁ y² c (1a)

Example - Kitchen Exhaust Hood

Required air volume in a exhaust hood with circumference 3 m, 1.2 m above the stove, can be calculated like

q = 2  0.2 (m/s) 1.2² m²  3 (m)

= 1.7 m³/s

Exhaust Hood Calculator

The air flow volume in the exhaust hood can be calculated below

capture velocity - v₁ - (m/s)

vertical distance from table to hood - y - (m)

circumference exhaust hood - c - (m)

Exhaust Hood with internal Plate

The efficiency of an exhaust hood can be improved by adding an internal plate.

The required air volume for an exhaust hood with a plate can in general be reduced to approximately 80% compared to an exhaust hood without a plate.

Exhaust Hood with Side Walls

The exhaust hood efficiency can be further improved by adding side walls.

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