JH - IOG - RCC Book Questions

Terms in this set (76)

The five stages of combustion are:

Induction

Heat is initially supplied by an external source which results in production of flammable vapour.

These vapours mix with air above the fuel and, if sufficient energy is provided, the combustion reaction begins between the vapour and the oxygen.

Ignition

The point of ignition is reached when the reaction becomes self-sustaining (and no longer requires an external heat source).

At this stage combustion develops very quickly and there is a dramatic increase in temperature as the fire grows.

Growth

Once ignited, the fire may spread through direct burning or through the typical mechanisms of heat transmission (convection, conduction or radiation).

The rate, scale and pattern growth depend on a number of factors such as:

The nature, form and amount of oxygen (open, ventilated versus sealed containment); the amount of heat produced by the reaction.

Steady State

After the growth period the temperature stabilises and the combustion process reaches a steady state where the reaction between fuel and oxygen is balanced until all the fuel is consumed.

Decay

Decay will begin when either the fuel or oxygen has been consumed.

The fire will extinguish and gradually cool down.
In the early stages of decay, there is still a considerable amount of heat; there is certainly enough to cause re-ignition if more fuel or oxygen is supplied.

In the latter case, admission of oxygen (e.g. opening a window) into an oxygen-depleted room can result in a sudden explosive re-ignition of vapours.
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