Combustibility groups and classes: we understand the terminology together with Promat. Classification of building materials by fire hazard Designation of groups of combustible building materials by combustibility

Substances and materials are combustible if they are able to ignite spontaneously, as well as ignite from an ignition source and burn independently after its removal.

In turn, all combustible materials are included in one or another combustibility group.

The essence of the method for determining combustibility groups is to determine the degree of damage to the material, the time of self-burning, the temperature of the flue gases at a fixed thermal effect on the samples in the combustion chamber.

Combustible building materials (according to GOST 30244), depending on the values of the combustibility parameters, are divided into four combustibility groups: G1, G2, G3, G4 in accordance with the table below. Materials belong to a certain combustibility group, provided that all the values of the parameters set by the table for this group correspond.

Flammability parameters
Combustibility group of materials	Flue gas temperature T, WITH	Degree of damage along the length S L ,%	Degree of damage by weight S m, %	Duration of self-burning t c.r , With
G1	≤135	≤65	≤20	0
G2	≤235	≤85	≤50	≤30
G3	≤450	>85	≤50	≤300
G4	>450	>85	>50	>300

Note - For materials of combustibility groups G1 - G3, the formation of burning melt drops during testing is not allowed.

For testing in the FGBU SEU FPS IPL in the Republic of Mordovia, it is necessary to provide 12 samples with dimensions of 1000 × 190 mm. The thickness of the samples should correspond to the thickness of the material used in real conditions. If the thickness of the material is more than 70 mm, the thickness of the specimens shall be 70 mm. During the preparation of samples, the exposed surface should not be processed.

Testing of samples is carried out in the thermophysical laboratory at the Shaft Furnace test facility.

(1 - combustion chamber; 2 - sample holder; 3 - sample; 4 - gas burner; 5 - air supply fan; 6 - combustion chamber door; 7 - diaphragm; 8 - ventilation tube; 9 - gas pipeline; 10 - thermocouples; eleven - exhaust hood; 12 - viewing window).

During the tests, the temperature of the flue gases and the behavior of the material under thermal exposure are recorded.

After the end of the test, the length of the segments of the undamaged part of the samples is measured and their residual mass is determined.

The intact part of the sample is considered to be that which has not burned or charred either on the surface or inside. Soot deposition, discoloration of the sample, local chipping, sintering, melting, swelling, shrinkage, warping or change in surface roughness are not considered damage. The measurement result is rounded to the nearest 1 cm.

The undamaged part of the samples remaining on the holder is weighed. The weighing accuracy must be at least 1% of the initial mass of the sample.

Processing of the results is carried out according to the method of GOST 30244-94.

After testing and paying the cost of the test, the employees of the testing fire laboratory prepare reporting documentation.

Fire and explosion hazard conditions when using substances and materials

To ensure the fire and explosion safety of the processes of production, processing, storage and transportation of substances and materials, it is necessary to use data on the indicators of fire and explosion hazard of substances and materials with the safety factors given in Table. 3

Way to prevent fire, explosion	Regulated parameter	Fire and explosion safety conditions
Prevention of the formation of a combustible environment


Limitation of flammability and combustibility of substances and materials	Flammability of a substance (material)	Flammability of a substance (material) should not be more regulated
Prevention of education in
combustible environment (or introduction into
her) ignition sources

Reproducibility of the method for determining the fire hazard index at a confidence level of 95%;

Safe temperature, °С;

Permissible flash point, °С;

Flash point in a closed crucible, °С;

The minimum temperature of the medium at which spontaneous combustion of the sample is observed, °С;

Smoldering temperature, °С;

Safe ignition energy, J;

Minimum ignition energy, J:

Upper concentration limit of flame propagation through a mixture of combustible substance with air, % vol. (g m -3);

Minimum explosive oxygen content in the combustible mixture, % vol.;

Safe concentration of oxygen in the combustible mixture, % vol.;

The minimum phlegmatizing concentration of the phlegmatizer, % vol.;

Safe phlegmatizing concentration of phlegmatizer, % vol.

By combustibility, substances and materials are divided into three groups: non-combustible, slow-burning and combustible.

Non-combustible (slow-burning) - substances and materials that are not capable of burning in air. Non-flammable substances can be fire and explosion hazard.

Slow-burning (slow-burning) - substances and materials capable of burning in air when exposed to an ignition source, but not capable of burning independently after its removal.

combustible (combustible)- substances and materials capable of spontaneous combustion, as well as ignite when exposed to an ignition source and burn independently after its removal.

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, as well as vapors of flammable and combustible liquids.

Flammable liquids (FL) - Substances capable of self-burning after removal of the ignition source and having a flash point not higher than 61°C (closed cup) or 66°C (open). Such liquids include individual substances: acetone, benzene, hexane, heptane, dimethylformamide, difluorodichloromethane, isopentane, isopropylbenzene, xylene, methyl alcohol, carbon disulfide, styrene, acetic acid, chlorobenzene, cyclohexane, ethyl acetate, ethylbenzene, ethyl alcohol, as well as mixtures and technical products gasoline, diesel fuel, kerosene, white spirit, solvents.

Flammable liquids (GZH) - Substances capable of spontaneous combustion after removal of the source of ignition and having a flash point above 61° (closed cup) or 66° C (open cup). 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 explosives with it.

3 Classification of premises for fire safety

In accordance with the "All-Union norms of technological design" (1995), buildings and structures in which production is located are divided into five categories (table 5).

	Characteristics of substances and materials located (circulating) in the room
explosion-fire-dangerous	Combustible 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, upon ignition of which the estimated overpressure of the explosion in the room exceeds 5 kPa. Substances and materials capable of exploding and burning when interacting with water, atmospheric oxygen or one with the other in such an amount that the calculated overpressure of the explosion in the room exceeds 5 kPa.
explosive fire-hazardous	Combustible dusts or fibres, flammable liquids with a flash point of more than 28 ° C, flammable liquids in such an amount that they can form explosive dust or vapor-air mixtures, upon ignition of which an estimated excess explosion pressure in the room develops in excess of 5 kPa.
flammable	Combustible and slow-burning liquids, solid combustible and slow-burning substances and materials that can only burn when interacting with water, atmospheric oxygen or one with the other, provided that the premises in which they are available or circulated do not belong to categories A or B
	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, combustible gases, liquids and solids that are burned or disposed of as fuel
	Non-flammable substances and materials in a cold state

Category A: shops 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 battery plants, hydrogen stations, etc.

Thermal insulation materials in terms of security fire safety characterized by flammability properties.

There are non-combustible (NG group) and combustible materials, which, in turn, are divided into: G1 - slightly combustible, G2 - moderately combustible, G3 - normal combustible, G4 - highly combustible.

Building materials are classified as non-combustible (stone of natural origin, cement concrete, glass, metal products) with the following values of combustibility parameters determined experimentally: temperature increase - no more than 50 degrees Celsius, sample mass loss - no more than 50%, duration of stable flame burning - no more than 0 seconds.

Combustible building materials are divided into the following groups:
1) Slightly combustible (G1), having a flue gas temperature of not more than 135 degrees Celsius, the degree of damage along the length of the test sample is not more than 65%, the degree of damage by weight of the test sample is not more than 20%, the duration of self-burning is 10 seconds. Slightly combustible include: asphalt concrete, gypsum and concrete materials containing an organic filler of more than 8% by weight, mineral wool boards on a bituminous binder with its content from 7 to 15%, etc.

2) moderately flammable (G2), having a flue gas temperature of not more than 235 degrees Celsius, the degree of damage along the length of the test sample is not more than 85%, the degree of damage by weight of the test sample is not more than 50%, the duration of self-burning is not more than 30 seconds;

3) normally combustible (HC), having a flue gas temperature of not more than 450 degrees Celsius, the degree of damage along the length of the test sample is more than 85%, the degree of damage by weight of the test sample is not more than 50%, the duration of independent combustion is not more than 300 seconds;

4) highly combustible (G4), having a flue gas temperature of more than 450 degrees Celsius, the degree of damage along the length of the test sample is more than 85%, the degree of damage by weight of the test sample is more than 50%, the duration of self-burning is more than 300 seconds.

For materials belonging to the combustibility groups G1-GZ, the formation of burning melt drops is not allowed. For materials belonging to the combustibility groups G1 and G2, the formation of melt drops is not allowed. For non-combustible building materials, other fire hazard indicators are not determined and not standardized.

All organic materials, such as wood, belong to the combustible group, and their fire hazard increases with the addition of various polymers. For example, paints and varnishes not only increase combustibility, but also contribute to a more rapid spread of flame over the surface, increase smoke generation and toxicity. To reduce the fire hazard of organic building materials, as in the case of polymeric substances, they are treated with flame retardants. applied to the surface, under the influence high temperatures flame retardants may foam or release non-flammable gas.

One of the central places is occupied by a fire hazard assessment and a competent choice of building materials based on current norms and standards and taking into account functional purpose and individual features of the building.

According to experts, the combustibility group of the material is not the main criterion for choosing a heater, since the fire hazard class is important for the design. And it is determined on the basis of natural tests. Very often, even combustible materials make it possible to achieve the required indicators of the fire hazard of the structure.

Classification of building materials

By origin and destination

By origin, building materials can be divided into two groups: natural and artificial.

natural called such materials that are found in nature in finished form and can be used in construction without significant processing.

artificial called building materials that are not found in nature, but are manufactured using various technological processes.

According to their purpose, building materials are divided into the following groups:

Materials intended for the construction of walls (brick, wood, metals, concrete, reinforced concrete);

Binders (cement, lime, gypsum) used to produce non-fired products, masonry and plaster;

Thermal insulation materials (foam and aerated concrete, felt, mineral wool, foam plastics, etc.);

Finishing and facing materials(rocks, ceramic tiles, different kinds plastics, linoleum, etc.);

Roofing and waterproofing materials(roofing steel, tiles, asbestos-cement sheets, slate, roofing felt, ruberoid, isol, brizol, poroizol, etc.)

NON-COMBUSTABLE BUILDING MATERIALS

natural stone materials. Natural stone materials are called building materials obtained from rocks through the use of only machining(crushing, sawing, splitting, grinding, etc.). They are used for the construction of walls, floors, stairs and building foundations, cladding of various structures. In addition, rocks are used in the production of artificial stone materials (glass, ceramics, heat-insulating materials), as well as raw materials for the production of binders: gypsum, lime, cement.

The effect of high temperatures on natural stone materials. All natural stone materials used in construction are non-combustible, however, under the influence of high temperatures, various processes occur in stone materials, leading to a decrease in strength and destruction.

Minerals included in stone materials have different coefficients of thermal expansion, which can lead to internal stresses in the stone during heating and the appearance of defects in its internal structure.

The material undergoes a modification transformation of the structure of the crystal lattice associated with an abrupt increase in volume. This process leads to cracking of the monolith and a drop in the strength of the stone due to large thermal deformations resulting from sudden cooling.

It should be emphasized that all stone materials under the influence of high temperatures lose their properties irreversibly.

Ceramic products. Since all ceramic materials and products are fired at high temperatures during their production, repeated exposure to high temperatures under fire conditions does not significantly affect their physical and mechanical properties if these temperatures do not reach the softening (melting) temperatures of the materials. Porous ceramic materials (ordinary clay brick, etc.), obtained by firing without being brought to sintering, can be exposed to moderately high temperatures, as a result of which some shrinkage of structures made from them is possible. The impact of high temperatures during a fire on dense ceramic products, which are fired at temperatures of about 1300 ° C, practically does not have any harmful influence, since the temperature in the fire does not exceed the firing temperature.

Red clay brick is the best material for the installation of fire walls.

Metals. In construction, metals are widely used for the construction of frames for industrial and civil buildings in the form of rolled steel profiles. A large amount of steel is used to make reinforcement for reinforced concrete. Steel and cast-iron pipes, roofing steel are used. IN last years light building structures made of aluminum alloys are being used more and more widely.

Behavior of steels in a fire. One of the most characteristic features all metals - the ability to soften when heated and restore their physical and mechanical properties after cooling. During a fire, metal structures heat up very quickly, lose strength, deform and collapse.

Reinforcing steels (see the "Reference Materials" section) will behave worse in fire conditions, which are obtained by additional hardening by heat treatment or cold drawing (hardening). The reason for this phenomenon is that these steels receive additional strength due to crystal lattice distortion, and under the influence of heating, the crystal lattice returns to an equilibrium state and the increase in strength is lost.

aluminum alloys. The disadvantage of aluminum alloys is a high coefficient of thermal expansion (2-3 times higher than that of steel). When heated, it also a sharp decline their physical and mechanical properties. The tensile strength and yield strength of aluminum alloys used in construction are reduced by about half at a temperature of 235-325 °C. Under fire conditions, the temperature in the room volume can reach these values in less than one minute.

Materials and products based on mineral melts and products from glass melts. This group includes: glass materials, products from slag and stone casting, glass-ceramics and slag glass-ceramics, sheet window and display glass, patterned, reinforced, solar and heat-shielding, facing glass, glass profiles, double-glazed windows, glass mosaic tiles, glass blocks, etc.

Behavior of materials and products from mineral melts at high temperatures. Materials and products made from mineral melts are non-combustible and cannot contribute to the development of a fire. Exceptions are materials based on mineral fibers containing some organic binder, such as thermal insulation mineral boards, silica boards, basalt fiber boards and rolled mats. The combustibility of such materials depends on the amount of binder introduced. In this case, its fire hazard will be determined mainly by the properties and amount of the polymer present in the composition.

Window glass does not withstand prolonged heat loads during a fire, but with slow heating it may not break down for quite a long time. The destruction of glass in light openings begins almost immediately after the flame begins to touch its surface.

Structures made of tiles, stones, blocks, obtained on the basis of mineral melts, have a significantly higher fire resistance than sheet glass, since, even after cracking, they continue to bear the load and remain sufficiently impervious to combustion products. Porous materials from mineral melts retain their structure almost to the melting point (for foam glass, for example, this temperature is about 850 ° C) and perform heat-shielding functions for a long time. Since porous materials have a very low coefficient of thermal conductivity, even at the moment when the side facing the fire melts, deeper layers can perform heat-shielding functions.

COMBUSTIBLE BUILDING MATERIALS

Wood. When wood is heated to 110 ° C, moisture is removed from it, and gaseous products of thermal destruction (decomposition) begin to be released. When heated to 150 ° C, the heated surface of the wood turns yellow, the amount of volatile substances released increases. At 150-250 ° C, wood acquires Brown color due to charring, and at 250-300 ° C, the products of wood decomposition ignite. The self-ignition temperature of wood is in the range of 350-450 °C.

Thus, the process of thermal decomposition of wood proceeds in two phases: the first phase - decomposition - is observed when heated to 250 ° C (to the ignition temperature) and proceeds with the absorption of heat, the second, the combustion process itself, proceeds with the release of heat. The second phase, in turn, is divided into two periods: the combustion of gases formed during the thermal decomposition of wood (the fiery phase of combustion), and the combustion of the resulting charcoal (the smoldering phase).

Bituminous and tar materials. Building materials, which include bitumen or tar, are called bituminous or tar.

Ruberoid and roofing felt roofs can catch fire even from low-power sources of fire, such as sparks, and continue to burn on their own, emitting a large amount of thick black smoke. When burning, bitumen and tar soften and spread, which significantly complicates the situation in a fire.

The most common and effective way reducing the flammability of roofs made of bituminous and tar materials is sprinkling them with sand, backfilling with a continuous layer of gravel or slag, covering with any non-combustible tiles. A certain fire-retardant effect is obtained by coating rolled materials with foil - such coatings do not ignite under the influence of sparks.

It should be borne in mind that rolled materials made using bitumen and tar are prone to spontaneous combustion when rolled up. This circumstance must be taken into account when storing such materials.

polymer building materials. Polymer building materials (PSM) are classified according to various criteria: type of polymer (polyvinyl chloride, polyethylene, phenol-formaldehyde, etc.), production technology (extrusion, molding, roller-calender, etc.), purpose in construction (structural, finishing, materials for floors , heat and sound insulating materials, pipes, sanitary and molded products, mastics and adhesives). All polymeric building materials are highly combustible, smoke generating and toxic.

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Fire and explosion hazard conditions when using substances and materials

3 Classification of premises for fire safety

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Combustibility groups and classes: we understand the terminology together with Promat. Classification of building materials by fire hazard Designation of groups of combustible building materials by combustibility

Fire and explosion hazard conditions when using substances and materials

3 Classification of premises for fire safety

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