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Based on nature and intensity combustions are classified into three types. They are:
(i) Rapid combustion
(ii) Spontaneous combustion
(iii) Explosion

Flame: It is a zone or burning vapour. The substances which vaporise during
burning give flames.

Example: Kerosene oil and molten wax. Inflammable substances have very low ignition temperature. Fire can be controlled by removing one or more requirements essential for producing fire. Water is commonly used to control fires. Water cannot be used to control fires involving electrical equipments or oils.

There are three different zones of a flame – dark zone, luminous zone and non-luminous zone.

Fuel is any material that is burned to obtain energy that can be used to heat or
A good fuel must:

Oxides of sulphur and nitrogen produced by the burning of coal, diesel and
petrol cause Acid rain which is harmful for crops, buildings and soil.

Be readily
available. Be cheap. Burn easily at a moderate rate.

Produce a large amount of heat. • Not leave behind any undesirable
Fuels differ in their efficiency and cost. Fuel efficiency is expressed in terms of its calorific value which is expressed in
units of kilo joule per kg.

Types of Fuels:
(i) Solid Fuels: Combustible substances which are solid at room
temperature.Example: coal, coke, wood, charcoal, etc. (ii) Liquid fuels: Volatile liquids which produce combustible vapour. Example:
Petrol,kerosene, alcohol, diesel, etc. (iii) Gaseous fuels: Combustible gases or mixture of combustible gases. Example:
Effects of Burning of Fuels:
(i) Carbon fuels like wood, coal petroleum release un burnt carbon particles. Theseare dangerous pollutants causing respiratory diseases, such as asthma.

(ii) Incomplete combustion of carbon fuels gives carbon monoxide which
is apoisonous gas.

(iii) Increased concentration of carbon dioxide in the air is believed to cause
globalwarming.

(iv) Oxides of Sulphur and nitrogen dissolve in rain water and form acids. Such
rain is Un burnt carbon particles in air are dangerous pollutants causing respiratoryproblems.

Incomplete combustion of a fuel gives poisonous carbon monoxide gas. Increased percentage of carbon dioxide in air has been linked to global warming.