Vocabulary. Combustion process

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Vocabulary

Combustion process – процесс горения

Combustible – легко воспламеняемый

Ignition - воспламенение

Heat - нагревание

Smouldering – медленное горение

Chain reaction – цепная реакция

Spread - распространяться

Ignition temperature – температура воспламенения

Carbonaceous - каменноугольный

Assume – принимать, допускать

Fuel - топливо

Intervene - вмешиваться

Flashover - вспышка

Critical stage – переломный момент

Combined - сочетать

Remove - устранять

Involve - подразумевать

Substance - вещество

Supporting combustion – поддерживающий горение

Chlorine - хлор

Ignited - разжигающий

Ignition stage – стадия воспламенения

Combustion process

The way a fire spreads with ordinary materials which are combustible depends on the time and rate in which the temperature increases. In the very beginning stage at ignition of the fire there is no heat to the fire except at the point where it ignites and the small amount of chemical reactions do not produce much heat themselves. We call this second stage of the fire 'smouldering' and there is smoke but very little heat until the flames start-then the combustion process become faster and there is also more heat - this causes a chain reaction and the process changes. Then the flames spread and the amount of heat increases rapidly too.

The ignition temperature of most materials which are carbonaceous is between 40 and 1400 degrees Fahrenheit so it can then be assumed that the fire will then be making enough heat to burn all the fuels present, unless something intervenes to stop this. This stage is known as the 'flashover' or critical stage in the three phases of a fires development.

Fire control then involves the following combined actions: a) to remove the source of heat and the products resulting from the combustion, b) to channel and control the direction of the fire spread and c) to cool off the atmosphere and fuel so that the fire will stop burning. To be able to do this effectively requires an understanding of how the combustion process works.

We can define combustion, or fire, as a very fast chemical reaction between materials involving heat and light and we describe one of the substances as combustible, which means that it burns, and the other as supporting combustion, which in most ordinary fires is usually oxygen, although there are limited circumstances in which another substance such as chlorine can also support the process.

For a substance to be called combustible it means that it burns in air. For a fire to start anywhere there are three requirements: there must be a substance present which will burn quickly when combined with oxygen for example fuel. Secondly there must be enough oxygen to make the fuel burn when it is ignited - the more oxygen is present the more strongly the fire will burn. The third requirement is heat because most materials need a source of heat to ignite them, although it is not necessary to light all of the substance for the fire to begin and by lighting one area this will usually be enough at the ignition stage to start the process of combustion which will spread throughout the material.

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