How to Improve Ventilation

Ventilation has to do with air supply inside buildings.

Ventilation essentially is the replacement of used air by a supply of fresh outdoor air. It also deals with the quality of incoming air with regard to its temperature, humidity and purity. Good ventilation should ensure a thermal environment in the interiors that is comfortable and free from risk of infection.

• What happens to air in occupied rooms?
• A Change of Air
• Enhancing natural ventilation
• Artificial ventilation

There are some interesting aspects to the atmosphere within buildings, especially when occupied.

The changes in air in a confined place are both chemical and physical.

• When there people in a room more carbon di-oxide is released into their. It has been observed that in a mixed gathering each person exhales 0.6 c ft of carbon di-oxide every hour. These are the chemical changes involved.

• The room heats up perceptibly. Humidity increases because of the sweat and the exhaled air. Sweat also produces odour. The flow of air is impeded and this makes the room stuffy. People also release bacteria into the air, when they cough or sneeze. All these cause physical changes in the air.

• Apart from this, very specific pollutants are found inside rural and urban buildings. A Tata Energy Research Centre study observes "Key pollutants in urban buildings include nitrogen dioxide, carbon monoxide, radon (from building materials, water and soil), formaldehyde (from insulation), asbestos, mercury, man-made mineral fibres, volatile organic compounds, allergens and tobacco smoke - as well as health damaging organisms like bacteria."

• Many of us feel uncomfortable in crowded rooms without really being able to say what it is that annoys us. The above factors, apart from psychological, are responsible for this annoyance factor. In poorly ventilated rooms people feel unable to concentrate, complain of drowsiness and headaches. This is called the Sick Building Syndrome. People who live or work in such places are more prone to infection.

• A human being needs 3000 cft of fresh air each hour.
• Air Change: Air change is more important than the cubic space requirement. It is recommended that in a living room, there should be 2 or 3 air changes and in workroom there should be 4 to 6 air changes.
• Floor space: Floor space per person is equally important. The optimum floor space requirements per person vary from 50 to 100 sq. Ft.

A house should have the following devices to enhance natural ventilation.

Windows

Windows let in air. When a window and an open door (or a bigger window) are placed in line with each other unequal pressure is created and air moves from one opening to another. This is called cross ventilation and this ensures fresh air supply.

Screens, jalis

Air diffuses through fine meshes. These are preferred where privacy is required. But here the process is slow and needs to be supplemented with other types of ventilation.

Ventilators

These are excellent devices to keep the air circulating. They work on the theory of convection. Air flows from an area of high density to an area of low density; it rises when slightly heated and escapes from openings provided high up in the room and enters through inlets placed low. A narrow opening high up on the wall keeps the room cool in summer.

The following induce artificial ventilation:

• Exhaust Fans
• Centrifugal fans
• Air Conditioners

Air is extracted or exhausted to the outside by exhaust fans usually operated electrically. As air is exhausted, a vacuum is created which induces fresh air to enter the room through windows, doors and other inlets.

Centrifugal Fans

Fresh air is blown into the room by centrifugal fans so as to create a positive pressure and displace the used air. Sometimes centrifugal as well as exhaust fans are used.

Air Conditioning

Air conditioners are now used to keep temperatures down. Air conditioners were invented to purify air in the interiors. Air conditioning is becoming a popular cooling and ventilating system in homes.

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