Page 74 - Viva ICSE Science 5 : E-book

due to the formation of vapours. As the warmer air above the land rises up, the moisture
laden colder air, called the monsoon breeze, from the sea rushes on to the land and gets
heated. The heated moist breeze now rises up and becomes cooler while it is still over

the land. As the air becomes cooler it releases the moisture which falls on land as rain.

TIME TO REVISE

Write two lines on each of the following.
1. Distillation 2. Sedimentation 3. Land breeze

Role of ventilators

Ventilation is the process of continuous replacement of the foul air with the fresh air
inside a room. Ventilators and exhaust fans are

installed in our homes for this purpose.

Ventilation helps in removing unwanted smells
like that of cooking, cleaning, etc. Also, the

air that we breathe out or exhale is warm and
impure as it is rich in carbon dioxide. We know
that the warm air is lighter so it rises up and

the fresh air enters the room through doors
and window. As the air pressure inside the A well-ventilated house
room increases, the warm air rushes out through the ventilators. In this way, ventilation

replaces the impure air with the fresh air rich in oxygen that we need to breathe in.

Ventilation also removes the excess moisture present in the air. This keeps the walls, the
furniture and other stuff dry. Collection of moisture, however, can cause mould or fungi

to grow. Mould has negative eff ect on our health as it causes infection and also rotting
of things. Thus, we should keep our homes well-ventilated.

You can fi nd ventilators at the top of the walls of rooms at your home and school. These

may be in the form of small windows without doors and are usually two or more in
number. Sometimes exhaust fans are installed in these small windows. These fans face
outwards. They throw away the foul air out of the room. This air is replaced by the fresh

air that enters through the doors and windows. Thus, it is important to keep the windows
open for proper ventilation.

60