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8 INDUSTRIAL VENTILATION

8 .1 Overall Definitions

Ventilation is the mechanical system in a building that brings in "fresh"
outdoor air and removes the "contaminated" indoor air.
In the workplace, ventilation is used to control exposure to airborne
contaminants. It is commonly used to remove contaminants such as fumes, dust, and
vapours, in order to provide a healthy and safe working environment. Ventilation can
be accomplished by natural means (e.g., opening a window) or mechanical means
(e.g., fans or blowers).
Industrial systems are designed to move a specific amount of air at a specific
speed (velocity), which results in the removal (or "exhaust") of undesirable
contaminants. While all ventilation systems follow the same basic principles, each
system is designed specifically to match the type of work and the rate of contaminant
release at that workplace.
There are four purposes of ventilation:
1) Provide a continuous supply of fresh outside air.
2) Maintain temperature and humidity at comfortable levels.
3) Reduce the possibilities of fire or explosion hazards realization.
4) Remove or dilute airborne contaminants.
Why have an industrial ventilation system?
Ventilation is considered an "engineering control" to remove or control
contaminants released in indoor work environments. It is one of the preferred ways to
control employee exposure to air contaminants.
Ventilation systems are composed of many parts including:
1) an "air intake" area such as a hood or an enclosure,
2) ducts to move air from one area to another,
3) air cleaning device(s), and
4) fan(s) to bring in outside air and exhaust the indoor contaminated air.

8 . 2 T he B asic T ypes of V entilation S ystems

There are two types of mechanical ventilation systems used in industrial
settings:
1) General Dilution Ventilation reduces the concentration of the
contaminant by mixing the contaminated air with clean, uncontaminated air.
2) Local Exhaust Ventilation captures contaminates at or very near the
source and exhausts them outside.

 The main features of General dilution ventilation.

Dilution, or "general", ventilation supplies and exhausts large amounts of air
to and from an area or building. It usually involves large exhaust fans placed in the
walls or roof of a room or building.

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