Requirements and Types of Ventilation

VENTILATION REQUIREMENTS

The requirements of ventilation are shown in fig.

Health or permanent ventilation requirements

(a) Depletion of oxygen content - The amount of fresh air required for respiration is small and although this aspect cannot be neglected altogether, it can play only a very minor role in the ventilation design of buildings.

(b) Bacteria concentration - One criterion proposed for minimum ventilation standards is the elimination of the risk of infection by air-borne micro-organisms.

(c) Removal of vitiated air - In the case of the normal type of dwelling, contamination of air by hazardous gases such as carbon monoxide from heating appliances is not likely to be significant because such appliances are usually equipped with proper flues.

• The removal of air polluted by noxious or hazardous gases, vapours, dust and other contaminants produced by certain industrial processes generally requires special attention.

(d) Removal of odours - minimum standard of ventilation in spaces devoid of industrial contaminants seems to be the amount of fresh air required to reduce the concentration of unpleasant body and other odours to a level where they will no longer be objectionable.

All persons produce an of odour caused by sweat, sebaceous secretion, and foul breath. The nature and amount of odour given off varies from person to person since it is closely related to such factors as race, diet and living pattern, and although it is generally not harmful, odour may have an indirect effect on health by diminishing the appetite.

Further, the presence of odours in a room induces a feeling of stuffiness and discomfort. It is especially from a fresh noticeable to people entering such a room atmosphere. to amurotibus 2911вort 290mto gid tot botqobs

Comfort or Occasional ventilation requirements

(a) Removal of excess heat- Since excess heat liberated within occupied spaces combined with the net heat gain through the various structural elements, particularly in summer, contributes considerably to thermal discomfort, all excess heat should, as far as possible, be removed by ventilation.

(b) Air movement for body cooling - A part from the relatively high ventilation rates required for the removal of heat dissipated within the space, high air movements is also desirable under warm conditions for body cooling purposes.

(c) Ventilation for cooling or heating of structure - Another important purpose of ventilation that is closely related to comfort is the utilization of air flow during periods of low or high air temperature to cool or heat the structure and its contents. This can be achieved, particularly in more massive  structures in warm climates

Types Of Ventilation

The system of ventilation is classified into two types

1. Natural ventilation

2. Mechanical or artificial ventilation