VENTILATION is basically dilution of the occupied space by fresh outside air. A ventilation system involves in sweeping a particular space with relatively large quantities of air. This way, an improved environment can be achieved by controlling to some extent several parameters such as air motion, air purity and sometimes, air temperature.

• The term ‘Ventilation, as understood in Industries, generally covers the following :

• A) General Ventilation
• B) Controlling heat in Industrial Work Zones
• C) Industrial Exhaust Systems or Local Exhaust Ventilation

• A) GENERAL VENTILATION

• All working zones should have general ventilation for any one of the following reasons :
• 1) To supply fresh air for breathing,
• 2) To dilute the inside air with fresh outside air, this reduces the vitiation of the environment by body odours and also certain contaminants which may be given off during certain manufacturing operations
• 3) To provide heat balance for the body.

The supply of fresh air for breathing rarely calls for any special attention. Air entering the shop area by infiltration is usually more than sufficient to provide sufficient oxygen for the body. As regards the contamination of the environment by body odours, etc. this mostly depends upon the air space available for worker, and also the amount of physical activity. Generally, ventilation at the rate of 3 air changes per hour and above greatly minimizes vitiation of occupied space by body odours. Here, the air movement is also of vital importance. By air changes, it is meant , the volume of outside air allowed in the work zone compared with its own volume.

General Ventilation is also necessary to maintain heat balance of the body. This is especially so in hot locations more so when the conditions in the working area are worsened by heat given off from the manufacturing machinery. The normal body temperature should always be maintained at 37 deg.C., regardless of the physical activity of hot environment. Increased supply of fresh air into the working area will greatly relieve the heat loads . The heat dissipation from the body to its surroundings will depend upon the ambient dry bulb temperature , relative humidity and the radiated heat from the surrounding and also air movement.