5.2 Causes of emergency situation origin, stages of their development and hit site

The emergency situation appears as result of:

• rapid natural processes caused by gravity, earth circulation or temperature difference;

• effect of the external natural factors, which result in aging or corrosion of materials of constructions, structures and decreasing of physical-mechanical parameters;

• engineering-industrial defects of structures (designer's error; low quality of materials; breaking the rules of safety precautions for repairing and other works);

• influence of technological processes on materials of structures (overloading; high temperatures, vibration, aggressive medium);

• breaking of safety regulations of construction and technological processes, which induce kettle explosion, chemical substances spreading etc;

-military activity of all kinds.

Irrespective to the origin and type emergency situation development has four inherent stages (phases): origin, initiation, culmination and fading (liquidation of consequences).

At the origin stage the conditions, premise for future ES get formed: unfavorable natural processes are activated; the engineering-industrial defects of structures are accumulated, multiple technical breakdowns appear; equipment malfunctions.

To define duration of origin stage is possible approximately only by means of regular statistics of failures, breakdowns, «local» failures, observations of seismic, meteorological, mudflow struggling and other stations.

At the initiation stage of ES the most essential influence belongs to the human factor. Statistics testifies that more than 60% of accidents arise because of staff errors.

At the culmination stage releasing of energy or substance which makes unfavorable effect on people and environment occurs, at that moment the extreme situation appears. The characteristic emergency event is chain character of passing, when destructive action of the initiating event gets many times increased owing to engaging into the process powerful, toxic or biologically active components. It is the chain process of destroying energy and substances releasing.

The fading stage covers time from interception of the source of danger - localization of ES, to complete liquidation of its consequences, including all the chain of secondary, tertian and other consequences. The duration of this stage can make a year, and sometime a decade.

The knowledge of ES development chain in concrete conditions enables to reduce the risk for such situation originating to ensure readiness for emergency circumstances.

The territory on which the dangerous and harmful factors of ES act, with people, animals, structures, and communications located in is called as hit site. It is simple and complicated.

Simple hit site occurs under influence of one hit factor, for example, ruining from explosion, fire, only chemical or bacteriological contamination.

Complicated hit site arises owing to the force of several hit factors of ES. For example, the explosion at the chemical plant entails ruin, fire, chemical contamination of surroundings; earthquake and hurricane ruining structures can induce floods, fire from damage of an electrical network etc.

The shape of hit sites depends on a nature of a source of the dangerous factors and can be round on earthquake, explosion; band on hurricane, flood, mudflow; irregular on fire, tsunami and other.

Consequences can be various; they depend on type, character and scale of ES distribution.

Main consequences of ES are: death, disease of the people, ruin, radioactive polluting, chemical and bacteriological contamination. People who turned out to be in extreme conditions of ES get under affect of psycho-traumatic circumstance which induces violation of mental activity, the so called reactive condition. The reactive action of extreme conditions is made not only by direct danger for the life of the person, but also is connected with expectation of its realization outside the hit site.

If the radiuses of dangerous and harmful factors action can be defined beforehand by calculation methods, on contrary the radius of psychological action actually can vary. In some cases it can be many times larger than other hit factors radiuses.