Health Hygiene & Sanitation

Lesson 15 : Ventilation

Types Of Ventilation

• Natural ventilation


• Wind
• Inequality in temperature


• Mechanical/ Artificial ventilation


• Exhaust ventilation
• Plenum ventilation
• Balanced ventilation


• Air conditioning

Natural Ventilation

• Simplest system of ventilating


• Reliance is placed on natural factors


• Wind:


• Perflation: blow of wind
• Aspiration: suction force generated at the tail of wind around an obstruction
• Cross ventilation: presence of door/ windows opposite to each other


• Diffusion: when air passes through small openings. It takes long time for enough air to pass, so it can’t be relied up on.


• Inequality in Temperature:


• Air gets lighter density when heated and heavier density when cooled.
• Hot air moves up and cold air comes down and these generate ventilation


• Advantages:


• Less cost
• Simplest system
• With proper location, it can be utilised properly
• Disadvantages
• Not possible to regulate the velocity of the incoming air
• Not possible to regulate the temperature or humidity

Mechanical/ Artificial Ventilation

• Exhaust Ventilation:


• Air is extracted to the outside by exhaust fans
• Exhausted air creates a vacuum which induces fresh air to enter the room through windows/ doors
• Speed can be adjusted using the fans
• Local exhaust ventilation is used to remove dust and gases at their source of origin


• Plenum Ventilation:


• Air is blown to the INSIDE by centrifugal fans
• Propelled air creates a positive pressure which displaces vitiated air
• This system is of limited utility


• Balanced Ventilation


• Combination of both exhaust and plenum
• Both should match and balance to maintain suitable ventilation

Air conditioning

It is the simultaneous control of all or at least the FIRST THREE

• Temperature
• Humidity
• Air movement
• Distribution
• Dust
• Bacteria
• Odors
• Toxic gases

• Air conditioning


• Is particularly useful in operation theatres etc where strict control of air ensures less infections
• Air is filtered when drawn into an air-conditioner system from the room
• Excess humidity is removed, and excess air is re-circulated back into the room by adjusting the temperature
• Some percentage of fresh air is mixed with conditioned air


• Central Air conditioning


• Central air conditioning as employed in bigger hospitals etc is both economic and can be better regulated
• When the temperature between outside and inside is too high, a transition room to adjust before being exposed to excess difference in temperature.