Ignitions never just happen. This destructive physical phenomenon is preceded by the reaction of several components, which creates the conditions for the occurrence of combustion. It is on them that attention is drawn in our article. This issue is relevant, since life and health of people depend on compliance with security measures.
Reasons for the appearance
Fire occurs in cases where people violate the fire safety rules. It is the human factor that is the main reason for the appearance of such situations.
We list the conditions necessary for the occurrence of combustion: the presence of oxygen, a combustible substance, an ignition source. Some materials can ignite even without oxygen, for example, in an atmosphere of bromine or chlorine.
Important points
Combustible substances can be in the form of dust, gases, liquids, solid compounds. Sulfur, hydrogen, carbon, phosphorus, which are part of combustible materials, oxidize during combustion, forming decomposition products. They can pose a serious danger to human health and life. For example, inhalation for several minutes of hot air of 0.4% carbon monoxide (at 70 ° C) will be a lethal dose for people.
Thermal energy released during a fire has a devastating effect on process equipment and building structures. The result of such phenomena are explosions and accidents.
Since the conditions of combustion and fire are associated with the access of oxygen, it is important to exclude its intake to prevent the fire element. To do this is very problematic. Therefore, when thinking over fire-prevention measures, specialists try to use less combustible materials, to limit the likelihood of an ignition source.
Flammability classification
Depending on the combustibility, several groups are distinguished:
Fireproof (non-combustible), which are not carbonized and do not even smolder.
Difficult to burn - ignited by the ignition source, but after its removal can not burn on their own.
Combustible (combustible). Ignite when exposed to fire. After removing the provoking factor, they continue to burn on their own.
The group of flammable substances includes flammable materials and compounds. They need only 30 for ignition from an ignition source with minimum energy (sparks, matches, smoldering cigarettes, flames). Flammable liquids are considered to have liquids whose flash point does not exceed 61 ° C in a closed crucible.
A flash is a quick combustion of a mixture in which a transition to a stationary flame is not allowed. The fire propagation limit is related to the ability of building structures to burn independently. Many household materials are combustible, it is important to consider this when developing projects.
Fire is the enemy of man
In discussing what conditions are necessary for the occurrence of combustion, one cannot ignore the question regarding the consequences of fires.
If you are irresponsible in the process of life, do not comply with fire safety standards, try to use fire to destroy (armed conflicts, arson), lose control of the burning process, the flame will turn from a serious enemy.
Combustion factors
If the basic conditions for the occurrence of combustion are associated with the presence of oxygen, a source of ignition and a flammable substance, then the dangerous factors may be as follows:
burns of the respiratory tract at a high temperature of an air heated mass;
ignition by open fire of clothing, combustible materials;
loss of consciousness and death of a person due to inhalation of carbon monoxide;
poisoning of the body with toxic substances obtained by burning synthetic substances;
due to smoke, visibility decreases, difficulties arise when evacuating people;
when buildings collapse, human death is possible.
It is worth mentioning that, due to the damaging factors of the fire, objects and objects burn up, they are destroyed, carbonized, decommissioned.
Conditions for the occurrence of the combustion process: temperature and access of oxygen. If they are violated, deaths and destruction of technological equipment are possible.
Among the secondary consequences of fires, it is necessary to note the explosions, the leakage of toxic or polluting substances into the environment. Significant damage to rooms that have not been exposed to fire can be caused by water used to extinguish the source of ignition. Among the serious economic and social consequences can be highlighted the cessation of the functioning of an object of industrial importance.
Types of combustion
By this process is meant a chemical rapid reaction of oxidation or a combination of atmospheric oxygen and a combustible material. It is accompanied by the release of light, heat, gas.
However, there are other types of interactions. With some of them, light and heat can be generated even without the presence of oxygen. The combustion process can be not only a reaction of the compound, but also decomposition.
Fire, detonation, explosion are emitted. The conditions for burning in each of these options may vary. In the first situation, the flame propagation velocity is not more than 10 m / s, in the second - 100 m / s, for detonation - 1,000 m / s.
Considering the conditions of occurrence of combustion, we note that the use of pure oxygen significantly accelerates the process. When it decreases, the fire slows down. That is why, thinking over the conditions of occurrence and termination of combustion, it is important to take into account the percentage of oxygen in the mixture used (oxidizing agent), as well as the correct use of ignition sources, combustible materials. What can be done when a fire occurs? Here everything is based on one principle: if one of the three main factors is eliminated or the connection between them is broken, then the fire will stop.
Analyzing the conditions for the occurrence of the combustion process, we note that incomplete burning is the greatest danger to health. It is accompanied by the release of explosive and toxic mixtures.
PPB requirements
In order to maintain health and protect property from destruction, citizens must know and abide by the basic rules of fire safety. They are required to:
monitor the health of electrical wiring;
Do not litter balconies, basements, loggias with flammable materials;
know the rules for handling a fire extinguisher, other means of eliminating fires.
“List the conditions for the occurrence of combustion” - this question is addressed by the chemistry teacher to his students as part of the school course. Students not only list them, but also dwell on those safety rules, the observance of which guarantees the preservation of health. Moreover, adults should know them.
Useful Tips
It is important not only to know the causes of the occurrence - and what are the conditions for the cessation of burning, it is also necessary to learn, at least in order to take the first rescue steps.
If acetone, gasoline, or other flammable liquids light up in the house , you must use an air-foam fire extinguisher. If it is absent, a thick cloth or things previously moistened with water are used to eliminate the fire.
Also, to eliminate the source of ignition, you can use the method of overwhelming. Branches, clothes, sticks hit the edge of the resulting fire.
In case of flame detection, you must immediately contact the fire department.
Fire options
In the forest, sources can appear during careless human activities, as well as a result of natural phenomena (lightning). Such fires in hot, dry weather can take on the scale of a natural disaster. There are two types of fires: forest (horseback or grassroots) and peat.
The first option, as a rule, appears in deciduous forests. The speed of propagation of fire in such cases is negligible, the flame height reaches 2 meters. Coniferous forests are characterized by horse fires. In case of windy weather, the flame propagation speed reaches 25-30 km / h.
A second type of fire appears on natural or drained peatlands. They are characterized by prolonged smoldering of peat, the appearance of smoky air. This substance is a flammable mineral, therefore, the danger of such fires is high.
The results of statistical studies indicate that the human factor is the cause of more forest fires.
To prevent such a danger, it is necessary to strictly observe the fire regime, especially in the dry period, when the threat of rapid spread of fire is high.
Procedure for fire
Citizens must have primary means for extinguishing fires in buildings and premises that are their property. In the event of a fire, immediately report the incident to the fire department.
After the arrival of the rescue team, provide free access to eliminate the source of fire. In addition, it is expected that all resolutions, orders, and other legal requirements from officials of the fire and state supervision are enforced.
Fire fighting measures
When designing building structures, it is important to take into account the fact that fire can spread between buildings, as well as directly along them. It is necessary to provide for the separation of premises into fire compartments with special ceilings, to equip barriers for the subsequent spread of fire. Fire gates and doors are also organized.
There are certain requirements that apply to fire barriers in height and wall thickness. For example, the walls may not rise above the roof if combustible materials are used for its construction.
If the building is divided into fire compartments, then the fire wall should have a wall that has a wider and higher compartment.
It is allowed to place gates, doors, windows in the outer part of the fire wall with an abnormal fire resistance limit at certain distances: from the walls four meters — horizontally, from the roof more than eight meters — vertically.
In rooms with suspended ceilings, fire walls should divide the space above them.
To carry out the calculations, it is necessary to take into account that the floor area helps to extinguish the fire with various protective equipment for a time that would not exceed the time of loss of the bearing capacity by the main structural elements.
To eliminate or reduce the risk of fire spreading to nearby objects, there should be safe distances between structures and buildings called fire breaks.
Their sizes are determined taking into account the fire safety categories of the premises and the degree of fire resistance of the structures. At any enterprise, it is obligatory to conduct briefings for all employees with an entry in the journal on PPB.
What conditions of occurrence and cessation of combustion are explained in the safety rules, we found out. We hope that our article will help you protect yourself and your loved ones from such an insidious enemy as fire.