Theory of burning

Burning is chemical process in which a substance reacts with oxygen to produce a significant rise in temperature and the emission of light.

Key components for burning:

- flammable substance;

- oxidant (normally oxygen in air);

- igniter (impulse for ignition).

Types of burning by speed of fire spreading:

- deflagration – burning that spreads fire with the speed of dozens meters per second;

- explosion – hundred meters per second;

- detonation – thousands meters per second.

Types of processes that initiate burning:

- flash – rapid burning of inflammable mixture which is not followed with the flame;

- ignition – the act or process of initiating burning from igniter;

- self-ignition – thermal initiating burning without igniter;

- explosion – a violent release of energy resulting from a rapid chemical reaction, esp. one that produces a shock wave, loud noise, heat, and light.

FIRE AND EXPLOSION RISK INDEXES

I. Self-ignition point: the lowest temperature of a substance that causes self-ignition.

II. Concentration limits of ignition: lower and upper ones.

The lowest concentration of flammable gas or vapor at which it can already be ignited is called lower limit of ignition.

The highest concentration of flammable gas or vapor at which it can still be ignited is called upper limit of ignition.

III. Flashpoint: the lowest temperature of a substance that causes flash.

Using flash point flammable liquids are divided into two classes:

- high-inflammable: those with the flash point lower or equal 61 deg C, such as gasoline, spirit, acetone;

- inflammable: those with the flash point over 61 deg C, such as oil, black oil.

IV. Ignition point: the lowest temperature of the substance that causes ignition.

V. Temperature limits of ignition: temperatures corresponding to concentration limits.

VI. Flammability group:

- inflammable (flammable): liable to catch fire;

- hard-inflammable: liable to catch fire only in presence of igniter;

- nonflammable: unable to catch fire.

The indexes applicability for certain substance (table 4) depends on what aggregation state it has: liquid, gaseous, solid or dust.

Table 4

Applicability of fire-explosive indexes

Index	Fire-explosive indexes application for
	gas	liquid	solid	dust
Flammability group	+	+	+	+
Flash point	-	+	-	-
Ignition point	-	+	+	+
Self- ignition point	+	+	+	+
Lower (upper) concentration limits of ignition	+	+	-	-
Temperature limits of ignition	-	+	-	-