Rate of supply of fresh air
The quantity of fresh air to be supplied to a room depending on the use of a building.
The rate of supplying fresh air is decided by considering several factors such as a number of occupants, type of work, period of working, the age of occupants, etc.
Air movement (or air changes)
Air has to be moved or changed to cause proper ventilation of the space.
The rate of air change depends on the number of persons inside, room temperature, nature of the work, different room categories, and activities, etc.
Temperature of air
It is desirable that the incoming air for ventilation should be cool in summer and be warm in winter - before it enters the room.
Also the velocity of air is very important, including ventilation strategy, distribution pattern, etc.
The air contains certain amount of humidity.
It plays a significant role in the comfort of people affected by a ventilation system.
Natural or mechanical?
The air exchange from outside to inside of buildings happens in these ways - naturally or mechanically:
- Unintentional via air leakages from windows, doors, and various holes such as joints and cracks in the building envelope.
- Intentional via natural ventilation, through opening windows/doors and air vents for deliberate venting by people and for people.
- Proper mechanical/hybrid ventilation, to add additional and controllable airflow within buildings to provide a good indoor environment.