Flammability 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 flammable if they are capable of spontaneous combustion, 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 flammability group.

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

Combustible building materials (according to GOST 30244), depending on the values \u200b\u200bof the flammability parameters, are divided into four flammability groups: G1, G2, G3, G4 in accordance with the table below. Materials belong to a certain flammability group, provided that all the values \u200b\u200bof the parameters set in the table for this group correspond.

Flammability parameters
Flammability group of materials	Flue gas temperature T, FROM	Length of damage S L,%	Damage by weight S m, %	Duration of self-burning t c.r,from
D1	≤135	≤65	≤20	0
G2	≤235	≤85	≤50	≤30
G3	≤450	>85	≤50	≤300
G4	>450	>85	>50	>300

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

For testing at 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 the actual conditions. If the material is more than 70 mm thick, the specimen should be 70 mm thick. When making samples, the exposed surface should not be processed.

Samples are tested in a thermophysical laboratory at the Shakhtnaya Pech 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 influence are recorded.

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

The part of the specimen that is not burnt or charred, either on the surface or inside, is considered intact. Soot deposition, discoloration of the specimen, localized chipping, sintering, melting, swelling, shrinkage, warping or surface roughness are not considered as damage. The measurement result is rounded to the nearest 1 cm.

Weigh the undamaged portion of the samples remaining on the holder. The weighing accuracy should be at least 1% of the initial sample weight.

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

After testing and paying for the cost of testing, employees of the test 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 the fire and explosion hazard of substances and materials with the safety factors given in table. 3

Method of preventing fire, explosion	Regulated parameter	Fire and explosion safety conditions
Preventing the formation of a flammable environment


Limiting the flammability and combustibility of substances and materials	Flammability of the substance (material)	The flammability of the 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 indicator at a confidence level of 95%;

Safe temperature, ° С;

Flash point, ° С;

Flash point in a closed crucible, ° С;

The minimum temperature of the environment 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 a combustible substance with air,% vol. (g m -3);

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

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

The minimum phlegmatizing concentration of phlegmatizer,% vol .;

Safe phlegmatizing concentration of phlegmatizer,% vol.

In terms of 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 the air when exposed to an ignition source, but cannot independently burn 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 that can form 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 burn independently after removing the ignition source and have a flash point not higher than 61 ° С (in a closed crucible) or 66 ° (in an open one). These 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 (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 divided into five categories (Table 5).

	Characteristics of substances and materials located (circulating) in the room
explosion-hazardous	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, when ignited, the calculated excess pressure of the explosion in the room is exceeding 5 kPa. Substances and materials that can explode and burn when interacting with water, atmospheric oxygen or one with another in such an amount that the calculated excess pressure of the explosion in the room exceeds 5 kPa.
explosion-hazardous	Combustible dusts 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 or vapor-air mixtures, when ignited, the design overpressure of the explosion in the room, exceeding 5 kPa, develops.
fire hazardous	Flammable and hardly combustible liquids, solid combustible and hardly combustible 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 used do not belong to categories A or B
	Non-flammable 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
	Non-combustible substances and materials in a cold state

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 battery installations, hydrogen stations, etc.

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

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

Building materials are non-flammable (natural stone, concrete made of cement, glass, metal products) with the following values \u200b\u200bof flammability parameters determined experimentally: temperature increase - no more than 50 degrees Celsius, sample weight loss - no more than 50%, duration of stable flame burning - no more than 0 seconds.

Combustible building materials are classified into the following groups:
1) Slightly flammable (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 the mass of the test sample is not more than 20%, the duration of self-burning is 10 seconds. Low-flammable materials include: asphalt concrete, gypsum and concrete materials containing organic filler more than 8% of the mass, mineral wool slabs on a bituminous binder with a content of 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 the mass of the test sample is not more than 50%, the duration of self-burning is not more than 30 seconds;

3) normally combustible (GZ), 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 the mass of the test sample is not more than 50%, the duration of self-combustion is not more than 300 seconds;

4) highly flammable (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 the mass of the test sample is more than 50%, the duration of self-combustion is more than 300 seconds.

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

All organic materials, for example wood, belong to the combustible group, and their fire hazard increases with the addition of various polymers. For instance, paints and varnishes not only increase flammability, but also contribute to a more rapid spread of the 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 fire retardants. Applied to the surface, under the influence high temperatures flame retardants can foam or release non-flammable gas.

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

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

Classification of building materials

By origin and purpose

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

Natural refers to materials that occur in nature in finished form and can be used in construction without significant processing.

Artificial they call building materials that do not occur in nature, but are manufactured using various technological processes.

By purpose, building materials are divided into the following groups:

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

Binder materials (cement, lime, gypsum) used to obtain non-fired products, masonry and plaster;

Thermal insulation materials (foam and aerated concrete, felt, mineral wool, foams, 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, roofing felt, isol, brizol, poroizol, etc.)

NON-FLAMMABLE BUILDING MATERIALS

Natural stone materials. Natural stone materials are building materials obtained from rocks through the use of only mechanical processing (crushing, sawing, splitting, grinding, etc.). They are used for the construction of walls, flooring, 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 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 in stone materials, various processes occur, leading to a decrease in strength and destruction.

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

The material undergoes a modification transformation of the crystal lattice structure 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 temperature deformations resulting from sudden cooling.

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

Ceramic products. Since all ceramic materials and products in the process of their production are fired at high temperatures, the repeated action of 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, which is not brought to sintering, can succumb to moderately high temperatures, as a result of which some shrinkage of structures made of them is possible. The effect of high temperatures in a fire on dense ceramic products, which are fired at temperatures of about 1300 ° C, practically does not have any harmful influence, since the fire temperature does not exceed the firing temperature.

Red clay brick is the best material for the construction 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. They use steel and cast iron pipes, roofing steel. IN last years lightweight building structures made of aluminum alloys are increasingly used.

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

Reinforcing steels will behave worse in fire conditions (see the section "Reference materials"), which are obtained by additional hardening by heat treatment or cold broaching (work hardening). The reason for this phenomenon lies in the fact that additional strength of these steels is obtained due to the distortion of the crystal lattice, 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 occurs a sharp decline their physical and mechanical indicators. The tensile strength and yield strength of aluminum alloys used in construction are approximately halved at 235-325 ° C. Under fire conditions, the room temperature can reach these values \u200b\u200bin less than one minute.

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

The behavior of materials and products from mineral melts at high temperatures. Materials and products made from mineral melts are non-flammable and cannot contribute to the development of a fire. Exceptions are materials made on the basis of mineral fibers containing a certain amount of organic binder, such as heat-insulating mineral plates, silica plates, slabs and roll mats made of basalt fiber. The flammability 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 in the composition.

Window glass does not withstand prolonged thermal loads in a fire, but with slow heating it may not collapse for a long time. Glass breakage in skylights begins almost immediately after the flame begins to touch its surface.

Constructions made of tiles, stones, blocks based on mineral melts have a significantly higher fire resistance than flat glass, since, even when cracked, 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 for a long time perform heat-shielding functions. 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.

FLAMMABLE BUILDING MATERIALS

Wood... When wood is heated to 110 ° C, moisture is removed from it, and gaseous products of thermal destruction (decomposition) begin to evolve. When heated to 150 ° C, the heated wood surface turns yellow, the amount of emitted volatile substances increases. At 150-250 ° C, wood acquires brown color due to charring, and at 250-300 ° C, wood decomposition products are ignited. The autoignition 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 heat absorption, the second, the combustion process itself, proceeds with the release of heat. The second phase, in turn, is subdivided into two periods: combustion of gases formed during the thermal decomposition of wood (flame phase of combustion), and combustion of the resulting charcoal (smoldering phase).

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

Ruberoid and tarpaulin roofs can ignite 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 on 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. Some fire-retardant effect is provided by the coating of roll materials with foil - such coatings do not ignite when exposed to sparks.

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

Polymeric building materials. Polymeric building materials (PSM) are classified according to various criteria: the type of polymer (polyvinyl chloride, polyethylene, phenol-formaldehyde, etc.), production technologies (extrusion, casting, roll-calender, etc.), purpose in construction (structural, finishing, floor materials , heat and sound insulation materials, pipes, sanitary and molded products, mastics and adhesives). All polymer building materials are highly flammable, smoke-generating and toxic.