All substances are divided into flammable, hardly combustible and non-combustible.

Substances that can burn independently after removing the ignition source are called combustible.

Substances that do not burn in air are called non-combustible.

An intermediate position is occupied by hardly combustible substances that ignite when exposed to an ignition source, but stop burning when it is removed.

All combustible substances are divided into the following main groups:

1. Combustible gases (GG)- Substances capable of forming flammable and explosive mixtures with air at temperatures not exceeding 50 ° C. GH includes individual substances: ammonia, acetylene, butadiene, butane, hydrogen, methane, carbon monoxide, propane, hydrogen sulfide, formaldehyde, as well as vapors of flammable and combustible liquids.

Flammable gases are explosive at any ambient temperature.

Distinguish:

Light gas: which at a temperature of 20 ° C and a pressure of 100 kPa has a density less than< 0,8 по отношению к плотности воздуха (т.е. относительную плотность).

Heavy gas:> 1.2. if the relative density is in between, both possibilities should be considered.

Liquefied gas: which, at a temperature below 20 ° C or a pressure above 100 kPa, or when both of these conditions are combined, turns into a liquid.

2. Flammable liquids (FL)- substances capable of burning independently after removing the ignition source and having a flashpoint not higher than 61 ° C (in a closed crucible). Such liquids include individual substances: acetone, benzene, hexane, heptane, xylene, methyl alcohol, carbon disulfide, styrene, acetic acid, chlorobenzene, ethyl alcohol, as well as mixtures and technical products: gasoline, diesel fuel, kerosene, solvents.

Explosives include flammable liquids, in which the flash point does not exceed 61 ° C, and the vapor pressure at a temperature of 20 ° C is less than 100 kPa (about 1 atm.).

3. Flammable liquids (FL)- substances capable of burning independently after removing the ignition source and having a flash point above 61 ° C (in a closed crucible) or 66 ° C (in an open one). GZh includes the following individual substances: aniline, hexyl alcohol, glycerin, ethylene glycol, as well as mixtures and technical products, for example, oils: transformer, vaseline, castor.

GZh with a flash point> 61 ° C are classified as fire hazardous, but heated under production conditions to a flash point and above are classified as explosive.

4. Combustible dust (HP)- solids in a finely dispersed state. HZ in the air (aerosol) is capable of forming explosive mixtures with it. Dust (airgel) deposited on walls, ceiling, surfaces of equipment is fire hazardous.

According to the degree of explosion and fire hazard, state enterprises are divided into four classes.

1 class- the most explosive - aerosols having a lower concentration limit of flammability (explosiveness) (NKPV) up to 15 g / m 3 (sulfur, naphthalene, rosin, mill dust, peat, ebonite).

2nd grade- explosive - aerosols with LEL value from 15 to 65 g / m 3 (aluminum powder, flour, hay, shale dust).

Grade 3- the most flammable - aerogels with an LEL value of more than 65 g / m 3 and a self-ignition temperature of up to 250 ° C (tobacco, elevator dust).

4th grade- fire hazardous - aerogels with an LEL value of more than 65 g / m 3 and a self-ignition temperature of more than 250 ° C (sawdust, zinc dust).

According to their combustibility, substances and materials are divided into three groups: non-combustible, hardly combustible and combustible.

Non-combustible (hardly combustible) - substances and materials not capable of burning in air. Non-flammable substances can be fire and explosive.

Flame retardant (hardly combustible) - substances and materials that can burn in air when exposed to an ignition source, but are not able to burn independently after its removal.

Combustible (combustible)- substances and materials that can ignite spontaneously, as well as ignite when exposed to an ignition source and burn independently after removing it.

All combustible substances are divided into the following main groups:

Combustible gases (GG) - substances capable of forming flammable and explosive mixtures with air at temperatures not exceeding 50 ° C. Combustible gases include individual substances: ammonia, acetylene, butadiene, butane, butyl acetate, hydrogen, vinyl chloride, isobutane, isobutylene, methane, carbon monoxide, propane, propylene, hydrogen sulfide, formaldehyde, and vapors of flammable and flammable liquids.

Flammable liquids (FL) - substances that can independently burn after removing the ignition source and have a flash point not higher than 61 ° C (in a closed crucible) or 66 ° (in an open one). These liquids include individual substances: acetone, benzene, hexane, heptane, dimethylforamide, difluorodichloromethane, isopentane, isopropylbenzene, xylene, methyl alcohol, carbon disulfide, styrene, acetic acid, chlorobenzene, cyclohexane, ethyl acetate, ethylbenzene technical products gasoline, diesel fuel, kerosene, white spirit, solvents.

Flammable liquids (FL) - substances that can burn independently after removing the ignition source and have a flash point above 61 ° (in a closed crucible) or 66 ° C (in an open). Flammable liquids include the following individual substances: aniline, hexadecane, hexyl alcohol, glycerin, ethylene glycol, as well as mixtures and technical products, for example, oils: transformer, vaseline, castor.

Combustible dust(/ 77) - solids in a finely dispersed state. Combustible dust in the air (aerosol) is capable of forming explosive

3 Classification of premises for fire safety

In accordance with the "All-Union Standards for Technological Design" (1995), buildings and structures in which production facilities are located are subdivided into five categories (Table 5).

Category A: workshops for the processing and use of metallic sodium and potassium, oil refining and chemical industries, warehouses for gasoline and cylinders for combustible gases, premises for stationary acid and alkaline storage systems, hydrogen stations, etc.

Combustible substances and materials are divided into three groups according to their flammability:

· Highly flammable;

· Substances of "medium flammability";

· Hardly flammable.

Flammable- flammable substances of increased fire hazard, which, when stored outdoors or indoors, are capable of igniting without preheating upon short-term (up to 30 s) exposure to a low-energy ignition source (from a match flame, spark, cigarette, heating of electrical wiring).

To flammable gases includes almost all combustible gases, for example, H 2, NH 4, CO, C 3 H 8, natural gas, etc.).

For flammable liquids(Flammable liquids) are flammable liquids with t flash. not> 61 0 С in a closed crucible (s.t.) or 66 0 С in an open crucible (o.t.), flammable liquids can be divided into three groups according to their fire hazard:

1. especially dangerous;

2. constantly dangerous;

3. dangerous at elevated temperatures.

1.To especially dangerous include, for example, acetone C 2 H 6 O, gasoline - B70, isopentane C 5 H 12, diethyl ether C 4 H 10 O, having t flash. not> 18 0 С (w.t.) or 13 0 С (r.t.). In the heat inside the vessel, the pressure rises; if the tightness is broken, the vapors of these liquids can spread at a considerable distance from the vessel, causing a fire.

2... Constantly dangerous flammable liquids are, for example, benzene C 6 H 6, toluene C 7 H 8, ethyl alcohol C 2 H 5 OH, dioxane C 4 H 8 O 2, ethyl acetate C 4 H 8 O 2 with t flash. from –18 0 to +23 0 (CC) or from –13 0 to 27 0 (RT) are characterized by the ability to form an explosive atmosphere in the vapor-air phase of closed vessels.

Table 1.1

Flammability classification of substances and materials

Notes to Table 1.1.

1 Spontaneous combustion is combustion that occurs in the absence of a visible ignition source. For example, oiled rags, metal shavings, sawdust, yellow phosphorus, vapor of liquid phosphorous hydrogen P 2 H 4 are capable of spontaneous combustion.

2 Wood mainly consists of fiber (C 6 H 10 O 5) n.

3 Rubber - unsaturated hydrocarbon (C 5 H 8) x, where x = 1000 ... 3000.

4 Rubber - rubber after mixing with sulfur, subjected to vulcanization (heating to a certain temperature).

5 Stearic acid C 18 H 36 O 2 (or C 17 H 35 COOH) - a combustible solid - a component of lard.

6 Petroleum products: gasoline, kerosene, naphtha, diesel fuel, lubricating oils, fuel oil, etc.

7 Alcohols: methyl CH 4 O, ethyl C 2 H 6 O (C 2 H 5 OH), n-propyl C 3 H 8 O; n-butyl C 4 H 10 O; n-amyl C 5 H 12 O, etc.

8 Acids: formic (methane) С 2 Н 2 О 2; acetic (ethane) C 2 H 4 O 2; oline (octadecene) O 2, etc.

9 Paraffins, conditional formula С 26 Н 54, are liquid and solid (melt when heated), are obtained from some types of petroleum products.

10 Liquid hydrocarbons: saturated (alkanes: pentane С 5 Н 12, hexane С 6 Р 14, etc.); unsaturated (alkenes: 1-pentene C 5 P 10, 1-hexene C 6 H 12, octene-1 C 8 H 16, etc.); cyclic (naphthenes: cyclopentane (CH 2) 5, cyclooctane (C 2 H 8) and others; aromatic (benzene C 6 H 6, toluene C 7 H 8, etc.).

11 Gaseous hydrocarbons: saturated (alkanes: methane CH 4, ethane C 2 H 6, propane C 3 H 3, butane C 4 H 10, etc.); unsaturated (ethylene C 2 H 4, propylene C 3 H 6, butylene C 4 H 8, etc.).

These features impose additional safety requirements for their transportation, storage and use.

3. To hazardous at elevated temperatures of flammable liquids include, for example, white alcohol C 10.5 N 21.3 lighting kerosene, chlorobenzene C 6 H 5 Cl, solvent, turpentine, etc., having a flash point above 23 0 ... 61 0 (w.t.) or 27 0 ... 66 0 (o.t.). In hot shops (at elevated temperatures), vapors of these liquids can ignite in air; at normal temperatures (~ 20 0 С), these substances ignite only in the presence of an ignition source.

Flammable solids (materials): celluloid, polystyrene, wood shavings, peat plates (ignited by the flame of a match, spirit lamp, gas burner).

Medium flammability: wood, coal, paper in bundles, fabric in rolls (requires a high-energy ignition source that can warm up to the ignition temperature).

Flammable: urea (carbamide) CH 4 ON 2, getinax grade B (pressed paper treated with synthetic resin of the resole type), wood after fire retardant treatment, PVC board.

A special class of combustible substances is pyrophoric and explosive substances.

Pyrophoric - capable of spontaneously igniting in the open air (liquid phosphorus, liquid phosphorous hydrogen P 2 H 4, etc.).

BB - substances capable of rapid exothermic transformation with the formation of compressed gases (explosion) without the participation of atmospheric oxygen (nitroglycerin, nitromethane, trinitrotuluene С 6 Н 2 (N 2 O) 3 СН 3, ammonium nitrate NH 4 NO 3).

Today mankind uses a wide variety of flammable substances. There are already quite a lot of them, and they all have their own unique characteristics. What are these substances? These are the raw materials that can continue to burn after the ignition source has been removed.

Gases and liquids

Today there are several groups of combustible substances.

You can start with the gases - GG group. This category includes those substances that can be mixed with air, thus forming an explosive or flammable environment, at a temperature not exceeding 50 ° C. This group of gases includes certain individual volatile compounds. It can be ammonia, acetylene, butadiene, hydrogen, isobutane and some others. Separately, it should be said that this also includes vapors that are released during the evaporation of flammable liquids (flammable liquids), which represent the following category.

The group of flammable liquids includes those liquid combustible substances that will continue to burn after the removal of the ignition source, and their flash point does not exceed the threshold of 61 degrees Celsius for a closed crucible. If this vessel is open, then the threshold will rise to 66 degrees. Such liquid substances include acetone, benzene, hexane, heptane, isopentane, styrene, acetic acid and many others.

Flammable liquids and dust

It would seem that fuel is one and the same, but in practice this turned out to be not the case. They fall into two different categories. Even despite the fact that the parameters of their ignition are the same and some liquids belong to both this and that group, there is a main difference. Oil-based substances are also referred to GJ. This, for example, can be castor or transformer.

Further, it should be said about such a flammable substance as dust. GP is a solid substance that is currently in a finely dispersed state. Getting into the air, such dust is capable of forming an explosive structure with it. If these particles settle on walls, ceilings, and other surfaces, they can cause a fire.

GP classes

Separately, it should be noted that there are classes of combustible substances and materials. For example, dust is divided into three categories depending on the degree of fire hazard and explosion hazard.

1. The first class is the most dangerous aerosols, in which the lower concentration limit of explosiveness (ignition) (LEL) is up to 15 g / m 3. These include sulfur, mill, ebonite or peat dust.
2. The second class includes those particles in which the LEL limit is in the range from 15 to 65 g / m 3. They are considered to be more explosive.
3. The third category is the most fire hazardous. This is a group of liquid aerogels, in which the LEL is more than 65 g / m 3, and the autoignition temperature is up to 250 degrees Celsius. Such properties are possessed by tobacco or elevator, for example, dust.

General characteristics

What are the flammable substances and why? There are several specific characteristics, possessing which, liquid, dust, gases and other substances can be classified as combustible.

For example, flash degree is a value that characterizes the lower temperature limit at which a liquid will form flammable vapors. However, it should be noted here that the presence of a fire source near such a vapor-air mixture will only cause its combustion, without a stable effect of combustion of the liquid itself.

If earlier it was said about the lower concentration limit, then there is also the upper one. NKPV or VKPV are, respectively, values, upon reaching which, an ignition or explosion of liquid, dust, gases, etc. can occur. All types of combustible substances have these limits. However, it is important to note here that if the concentration is lower or, conversely, higher than the specified limits, then nothing will happen even if there is a source of open fire in the immediate vicinity of the substance.

Solid raw materials

It should be said here that solid combustible substances behave somewhat differently than dust, liquid or gas. When heated to a certain temperature, this group of raw materials behaves individually, and this depends on its characteristics and structure. For example, if you take sulfur or rubber, then when heated, they first melt and then evaporate.

If you take, for example, coal or paper and some other substances, they begin to decompose when heated, leaving behind gaseous and solid residues.

Another very important point: the composition of combustible substances and their chemical formula strongly affects the actual combustion process itself. There are several stages into which this phenomenon is divided. Simple substances such as anthracite, coke or soot, for example, heat up and smolder without any sparks, since their chemical composition is pure carbon.

Complex ones include, for example, wood, rubber or plastic. This is due to the fact that their chemical composition is rather complex, and therefore there are two stages of their combustion. The first stage is the process of decomposition, which is not accompanied by the usual release of light and heat, but the second stage is already considered combustion, and at this time heat and light begin to be released.

Other substances and characteristics

Naturally, solids also have a flash point, but at the same time, for obvious reasons, it is much higher than that of liquid or gaseous substances. Flash point ranges are 50 to 580 degrees Celsius. It should be said separately that such a widespread combustible material as wood has a threshold of 270 to 300 ° C, depending on the species of the tree itself.

Gunpowder and explosives have the highest combustion rate among solids. This is due to the fact that both of these substances have a sufficiently large amount of oxygen, which is quite enough for their complete combustion. In addition, they can easily burn under water, underground, and in a completely sealed environment.

Wood

It is worth saying a little more about this combustible solid material, as today it is one of the most common. The reason for this is that it is one of the most affordable. It should be said here that in fact wood is a substance with a cellular structure. All cells are filled with air. The degree of porosity of any rock exceeds 50% and increases, which indicates that the concentration of solids is not too high in relation to air. It is because of this that it lends itself to burning well enough.

If we conclude, then we can say that in the world there is a large number of various flammable substances, which cannot be dispensed with in everyday life, but at the same time it is necessary to be extremely careful when using them only for their intended purpose.

Non-combustible materials are materials that, under the influence of fire or high temperatures, do not ignite, smolder or char. These include all natural and artificial inorganic materials, gypsum and concrete materials with an organic filler content of up to 8% by weight, mineral wool slabs with a synthetic, bitumen or starch bond content of up to 6% by weight, met

alla. Structures made of non-combustible materials are non-combustible. The buildings of the projected ATP are made of reinforced concrete structures, which are non-combustible.

Fire resistance is understood as the ability of building structures to resist high temperatures in a fire and at the same time maintain their operational functions. Its indicator is the fire resistance limit, determined by the time interval in hours from the beginning of the fire resistance test of the structure until one of the following signs appears:

the formation of through cracks or through holes in the structure through which combustion products or flame penetrate;

the temperature rise on an unheated surface is, on average, more than 160 ° C, or at any point on this surface, more than 190 ° C, compared to the temperature of the structure before testing, or more than 220 ° C, regardless of the temperature of the structure before testing;

loss of bearing capacity by the structure, i.e. collapse.

In terms of fire resistance, building structures according to SNiP 2.01.02-85 are divided into five degrees (I, II, III, IIIa, IIIb, IV, IVa and V). AAAAAAAAAAAAAAAAAAAAAAAAAAA

Fire resistance of buildings and structures is determined by the degree of fire resistance of their main structural elements. The buildings of the projected ATP in terms of material and type of structures are classified as fire resistance grade II.

An important property of building structures is their ability to resist the spread of fire, which is characterized by the limit of the spread of fire. This indicator is determined by the size of the damaged zone formed from the beginning of the standard fire test of samples until the appearance of one of the signs characterizing the fire resistance limit of the structure. The limit of fire propagation is measured in centimeters.

Category A includes explosive and fire hazardous. premises in which they are (circulate): flammable gases, flammable liquids with a flash point of not more than 28 ° C in such an amount that they can form explosive vapor-gas-air mixtures, when ignited, the calculated excess pressure of the explosion in the room exceeding 5 kPa ; substances and materials that can explode and burn when interacting with water, atmospheric oxygen or with each other in such an amount that the calculated excess pressure of the explosion in the room exceeds 5 kPa. At the ATP, the following premises can be classified as category A: painting, paint procurement; warehouse of paints and varnishes when using or storing organic solvents with a flash point of no more than 28 ° C; warehouse of fuel and lubricants when storing gasoline; acetylene; gas generator; battery charging room.

Category B includes explosive and fire hazardous premises containing: combustible dust or fibers; flammable liquids with a flash point of more than 28 ° C; flammable liquids in such an amount that they can form explosive dust-air or vapor-air mixtures, the ignition of which develops a calculated excess pressure of the explosion in the room, exceeding 5 kPa. At the ATP, the following premises can be classified as category B: painting; paint procurement; warehouse of paints and varnishes when using or storing organic solvents with a flash point above 28 ° C; warehouse of fuel and lubricants when storing flammable liquids with a flash point above 28 ° C.

Category B includes fire hazardous premises containing: flammable and hardly combustible liquids; solid combustible and hardly combustible substances and materials (including dust and fibers); substances and materials that can only burn when interacting with water, air oxygen or with each other, provided that the premises in which they are available or circulate do not belong to category A or B. woodworking, wallpaper and tire service areas; warehouses of rubber, auxiliary and lubricants.

Category D includes premises in which there are or are handling: non-combustible substances and materials in a hot, incandescent or molten state, the processing of which is accompanied by

the release of radiant heat, sparks and flames; flammable gases, liquids and solids that are burned or disposed of as fuel. The premises of the copper-radiator and forging-spring sections of the enterprise can be classified as category D.

Category D includes rooms in which non-combustible substances and materials in a cold state are located or circulate. This category includes premises: car wash stations; repair of batteries and electrical equipment; tin, metalwork and mechanical and aggregate sections; compressor room; warehouses of aggregates, metal, spare parts stored unpacked and without containers.

In the projected ATP, production and storage facilities belong to the following categories of fire hazard

Table no. 3.1.