According to statistics, from 10 to 20 thousand people per year die from fire, and property damage exceeds 5 billion rubles. Most of the fires come from the so-called human factor: an unquenched fire in the forest, an turned on iron turned on at home, matches in the hands of children, etc. Knowledge of the stages of the fire will help prevent or avoid a natural disaster.
Fire classification
Fire is uncontrolled burning. Ignitions have many types and classifications, which may depend on the following factors:
- zones and stages of fire;
- gas exchange capabilities (open or closed spaces);
- the state of combustible substances and materials (flammable and combustible liquids, gases, solid combustible substances , etc.);
- combustion propagation rates;
- facility (buildings, forests, peatlands, industrial zones, transport, etc.)
Fire conditions
Ignition occurs for many reasons. They are divided into two groups that have common characteristics.
The first group includes the human factor. Such a fire arises from inattentive or irresponsible behavior of people, non-compliance with safety measures during fire and gas welding, improper use of gas and electrical appliances, intentional arson.
The second group includes natural causes. Fire may result from lightning or spontaneous combustion.
Causes of Domestic Fire
Statistics say that 71% of fires occur in residential buildings due to people's faults. It could be:
- Operation of faulty or old electrical wires. As a rule, they have poor contacts at the junction, which leads to high electrical resistance. Therefore, the use of high power devices causes a short circuit in the wiring. The temperature at the junctions rises and a fire occurs.
- Misuse of the gas stove: drying the laundry over the flame of the gas appliance, curtains and towels, which are dangerously close to the burners.
- The use of flammable substances in everyday life without observing safety measures: the use of faulty gas cylinders, the storage of gasoline for garden equipment in a residential building, the improper use of combustible solvents during home repairs.
- Inappropriate monitoring of children. The child satisfies his curiosity by playing with fire. Careless movements and ignorance of risks leads to fires and injuries.
- The irresponsible behavior of smokers: sleeping with a lit cigarette in their mouths, burning cigarette butts thrown into dry grass or rubbish, etc.
Fire stages and their characteristics
The fire flares up gradually and has its stages of development:
- Elementary. The fire starts with a small fire and has the following characteristics: the burning center is small, the temperature is low, the flame height is low. Having basic knowledge and improvised means, a person can cope with fire on his own. For example, in a chemistry lesson, a teacher will extinguish a fire by throwing felt fabric on it, or a passerby will trample the grass that burst out of a cigarette butt.
- Developmental. The second stage of a fire is characterized by an increase in the area of combustion, an increase in temperature and height of the fire. For example, if in a summer cottage a fire spread from grass to trees and buildings, then more people and water are needed to extinguish.
- The developed stage. All fire characteristics: fire area , temperature and flame height, burning rate have maximum and constant value. At this stage of the fire, only professional firefighters with special equipment can handle the fire.
- Attenuation stage. This stage begins from the moment the rate of destruction of combustible materials decreases until the ceasefire is complete.
The main stages of the fire are characteristic of all types of fires, regardless of location, type of combustible materials, time of year or day.
Fire zones
The place where the fire occurs is conventionally divided into three zones:
- The combustion zone is the territory of the fire, which is characterized by the area of distribution, the height of the flame, the amount and speed of burning materials, the amount of heat released.
- The heat-affected zone is the place where the flame comes into contact with materials and structures. Fire, generating heat and acting on objects, modifies them or destroys them. A person cannot be in this zone without protective clothing.
- Smoke zone - a space that is filled with combustion products. The concentration of smoke leads to disorientation in space, which complicates the work of firefighters and poses a threat to human life.
Fire factors
Dangerous factors at any stage of the fire are phenomena that harm human health and lead to damage or loss of material values:
- Sparks and streams of flame. Intense fire flares up within 25-30 seconds. From this moment, depending on the area of the fire and combustion materials, the strength of thermal radiation increases. A high level of heat generation reduces the time during which the human body can withstand heat exposure. The highest criterion is 3,000 W / m. With such a flame intensity, pain occurs after 15 seconds, and after 40 seconds irreparable harm is caused to health.
- Heat flow and heat. During a fire, the air is heated not only at the site of ignition, but also in neighboring rooms. The temperature that the skin can withstand without damage to health is 45 ° C. At a temperature of 60-70 ° C, burns of the skin and mucous membranes appear after 15 minutes. The maximum time that the body can withstand at such temperatures is no more than an hour. At 100 ° C, a person can live 20 minutes, and at 150 ° C death immediately occurs due to burns of the respiratory system.
- Accumulation of toxic gases. Basically, in a fire, people die not from fire, but from carbon monoxide poisoning.
- Low oxygen. Oxygen starvation leads to lethargy, impaired coordination of movements, reduces the level of attention and concentration, which interferes with the effective work of rescuers.
- Smoke screen. Smoke disorientates a person in space and makes evacuation difficult. Smoldering particles that are in smoke corrode the eyes and mucous membranes.
These factors are the main causes of death. At any stage of the fire, it is important not to panic, but with clear actions to help yourself and others during the evacuation.