PRESSURISATION AND VENTILATION
PRESSURISATION AND VENTILATION
PRODUCT DESCRIPTION
The unsatisfactory past practices to providing exhaust ventilation without giving thought as to how the outdoor replacement air is to be provided has resulted in worker discomfort, damage to the costly and sophisticated equipments consequently the impaired in-plant environment in an industry. A present day awareness of this considers the need of providing suitable make up air systems by means of efficiently designed ventilation systems. The consideration of these factors will result in personnel comfort as well as a safe, controlled and dust free atmosphere.
Natural ventilation can seldom be satisfactory unless outside conditions are ideal and that rarely happens. A natural supply of fresh air depends upon the difference between the inside and outside temperatures. Fresh air will not flow naturally into a building unless a breeze is blowing in the direction, even then its distribution through an occupied space is a matter of chance. Nor will warm vitiated air flow out of the building unless the outside air is cooler than inside. Consequently, natural ventilation is least effective in a hot windless weather. Furthermore, there can be no defective control on the ingress of the dust inside the building spaces in the incoming air. Therefore, forced ventilation systems are necessary in most cases and in this context, three different systems may be employed as under:-
1. Extraction/ Exhaust of air
2. Supply of air
3. Combination of Extraction and supply
Supply Air System:-
In this system fresh air is blown into an occupied space by means of fans and the used air flows out through any available outlets due to pressurization effect. The advantages of the supply air systems are that fresh air is introduced into the occupied space in a positive manner and a reasonable control can be maintained over its distribution besides the process of recirculating interior air can be more conveniently achieved. In addition, the air pressure within the building which is slightly above that of the outside atmosphere, tends to prevent infiltration of outside air. For obtaining good distribution of fresh air it is necessary to provide uniform arrangement of air outlets.
Combination of Exhaust and Supply Systems:-
The fullest control of ventilation is achieved by using both supply and exhaust systems. Uniform distribution of fresh air supply can then be ensured and used air could be let out at convenient points according to the design requirements. Under such systems the input fans should be selected to give about 20% more air volume than the exhaust fans, thereby keeping the atmosphere in the building at higher pressure than outside and reducing the ill effects of infiltration due to dust and other air-borne contaminants.