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Spontaneous combustion is a phenomenon of the speed acceleration of
exothermic reactions, which causes a sudden temperature increase and burning of
matters in default of any inflammation source.
Spontaneous ignition is spontaneous combustion which is accompanied by
the appearance of the flame.
Burning can be accompanied by: fire and explosion.
The explosion is a rapid transformation of matter (explosive burning) which
is accompanied by the burst of energy and formation of shock wave (speed is of
330 m/s).
Explosion-proof indexes of substances and materials are used for:
 the analysis of the fire danger;
 classification of dangerous freights;
 the choice of the category of rooms and buildings pursuant to the
requirements of norms of the technological design;
 the purpose of the realization of technical supervision on materials.

Main causes of fires are:
1. Improper heat-producing machine installation – 20 %.
2. Faulty or improper installation of electrical installations and electrical
systems – 16 %.

3. Poor training equipment for repairing – 13 %.
4. Auto-ignition materials – 10 %.
5. Violation of the production process (especially at the end of the month).
6. Discharge static electricity.
7. Lighting strike.
Indexes of fire explosiveness of substances and materials:
 the combustibility group;
 flash temperature;
 combustion temperature;
 the lower and upper concentration borders of flame distribution;
 the conditions of thermal combustion.

Due to combustibility, matters and materials are divided into three groups:
1. Noncombustible (cannot be burned). Under fire effect or high temperature,
they do not flash, smolder, and char.
2. Heavily burnt. Under the fire effect or high temperature, they flash,
smolder, char and when the ignition source is available they continue to burn,
smolder or char.
3. Combustible (can be burnt). Under the fire effect or high temperature, they
flash, smolder, and char.

The main characteristic of liquids, which indicates its fire danger is the flash
point.
The flash point is the lowest temperature at which a mixture of vapors with
air is formed above its surface, capable of erupting from an external ignition pulse.

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