Room category b. Categories of buildings according to explosion and fire hazard

1. Based on fire and explosion hazards, industrial and warehouse premises, regardless of their functional purpose, are divided into the following categories:

1) increased fire and explosion hazard (A);

2) fire and explosion hazard (B);

3) fire hazard (B1 - B4);

4) moderate fire hazard (D);

5) reduced fire hazard (D).

2. Buildings, structures and premises for other purposes are not subject to division into categories.

3. Categories of premises for fire and explosion hazard are determined based on the type of flammable substances and materials located in the premises, their quantity and fire hazardous properties, as well as based on the space-planning solutions of the premises and the characteristics of the technological processes carried out in them.

4. Determination of categories of premises should be carried out by sequentially checking whether the premises belong to categories from the most dangerous (A) to the least dangerous (D).

5. Category A includes premises in which there are (circulate) flammable gases, flammable liquids with a flash point of no more than 28 degrees Celsius in such quantities that they can form explosive vapor-gas mixtures, upon ignition of which a calculated excess explosion pressure in the room develops, exceeding 5 kilopascals, and (or) substances and materials capable of exploding and burning when interacting with water, air oxygen or with each other, in such quantities that the calculated excess explosion pressure in the room exceeds 5 kilopascals.

6. Category B includes rooms in which flammable dusts or fibers are located (handled), flammable liquids with a flash point of more than 28 degrees Celsius, flammable liquids in such quantities that they can form explosive dust-air or steam-air mixtures, upon ignition of which the calculated excess explosion pressure in the room exceeding 5 kilopascals.

7. Categories B1 - B4 include premises in which flammable and low-flammable liquids, solid flammable and low-flammable substances and materials (including dust and fibers), substances and materials that can interact with water, air oxygen or only burn with each other, provided that the premises in which they are located (handled) do not belong to category A or B.

8. Classification of a room into category B1, B2, B3 or B4 is carried out depending on the quantity and method of placing the fire load in the specified room and its space-planning characteristics, as well as on the fire hazardous properties of the substances and materials that make up the fire load.

9. Category D includes premises in which non-combustible substances and materials are located (handled) in a hot, incandescent or molten state, the processing of which is accompanied by the release of radiant heat, sparks and flames, and (or) flammable gases, liquids and solids, which are burned or disposed of as fuel.

11. Categories of buildings and structures for fire and explosion hazards are determined based on the share and total area of ​​premises of a particular hazard category in this building or structure.

(see text in the previous edition)

12. A building belongs to category A if the total area of ​​category A premises in it exceeds 5 percent of the area of ​​all premises or 200 square meters.

13. A building does not belong to category A if the summed area of ​​category A premises in the building does not exceed 25 percent of the summed area of ​​all premises located in it (but not more than 1000 square meters) and these premises are equipped with automatic fire extinguishing installations.

14. A building belongs to category B if the following conditions are simultaneously met: the building does not belong to category A and the summed area of ​​premises of categories A and B exceeds 5 percent of the summed area of ​​all premises or 200 square meters.

15. A building does not belong to category B if the summed area of ​​premises of categories A and B in the building does not exceed 25 percent of the summed area of ​​all premises located in it (but not more than 1000 square meters) and these premises are equipped with automatic fire extinguishing installations.

16. A building belongs to category B if the following conditions are simultaneously met: the building does not belong to category A or B and the summed area of ​​premises of categories A, B, B1, B2 and B3 exceeds 5 percent (10 percent if the building does not have premises of categories A and B) the summed area of ​​all premises.

17. A building does not belong to category B if the summed area of ​​premises of categories A, B, B1, B2 and B3 in the building does not exceed 25 percent of the summed area of ​​all premises located in it (but not more than 3500 square meters) and these premises are equipped with automatic fire extinguishing

• laboratories;
• storerooms;
• utility room;
• archives.

Who determines the explosion hazard class of indoor areas?

Specialists from the design organization - a technologist or an electrical engineer - will help determine which category according to the PUE the premises belong to. First of all, the technician will determine the presence and number of different explosion and fire hazard zones in the room.

The following criteria are taken into account:

• name and characteristics of explosive and fire hazardous substances and materials stored in the premises;
• quantitative volume of an explosive mixture relative to the free volume of the room;
• the presence of technological equipment, during the operation of which it is possible to release gas or flammable liquids;
• footage of the room;
• other explosive factors.

Classification of explosion and fire hazardous zones and categorization of premises is carried out at the stage of development of project documentation, even before the start of construction work on the site.

Classes of hazardous areas of premises according to PUE

Based on whether a leak of an explosive mixture is possible during the operation of technological equipment, classes of explosive zones are identified in the room.

They also take into account the likely duration and frequency of the presence of the mixture in the room, establishing 3 types of leakage depending on this: constant, 1st and 2nd degree.

The explosion hazard zones in the room are classified as follows:

• 0 – presence of a dangerous gas mixture is observed for 1 hour or more;
• В-І – explosive mixtures are formed during normal operation of equipment;
• В-Іа – explosive mixtures are formed due to equipment malfunction or as a result of an accident;
• B-Ib – the same if GGs have a lower concentration limit (LCL) of 15% or more, a pungent odor, as well as production facilities that are associated with the circulation of hydrogen;
• V-Ig – areas near outdoor installations with GG, flammable liquids;
• B-II – during normal operation of the equipment, explosive mixtures are formed in a concentration of 65 g (or less) per 1 cubic meter;
• B-IIa – formation of an explosive mixture in a concentration of 65 g (or less) per 1 cubic meter. Possibly due to equipment damage or an accident.

The Rules provide exceptions that are possible when defining hazardous areas. The PUE describes in detail each zone class, and also gives the classes of zones of premises adjacent to the explosive zone of another room.

Classes of fire hazardous zones according to the PUE

According to the risk of fire in different areas of the room, they are divided into 4 classes:

• P-I – zones in rooms where gas liquids are located, having a flash t above 61 degrees;
• P-II - zones in rooms where the release of combustible dust or fibers with an LPQ of above 65 g per cubic meter is possible;
• P-IIa – zones in rooms where there are solid hot water in such quantities that the specific fire load is equal to 1 MJ per 1 sq. m. or more;
• P-III – outdoor zones where gas fluids are handled with a flash t above 61 degrees. (or solid HS).

Categories of premises according to explosion and fire hazard

The categorization of premises according to the PUE is carried out on the basis of the characteristics of substances and materials that circulate in the premises. In total, there are 5 main categories, which are designated by letters - from A to D, in order of decreasing explosion and fire hazard.

1. Category A premises have an increased fire and explosion hazard due to the fact that they contain highly flammable gases and flammable liquids.
2. Category B – explosion and fire hazardous premises.
3. Category B – fire hazardous premises. 4 subcategories – B1 – B4, which are determined by the value of the specific fire load.
4. Premises of category G are characterized by a moderate fire hazard; non-combustible substances (materials) are handled in them in a hot, incandescent or molten state.
5. Category D – premises of reduced fire hazard – non-flammable substances (materials) are used in a cold state.

The room category determined by the PUE, as well as the zone class, is indicated on a sign that is hung on the front door. For example, a sign with the designation “A/B-I” indicates that the room is characterized by an increased fire and explosion hazard and that during normal operation of the equipment, explosive mixtures are formed in it.

1.1. Categories of premises according to explosion and fire hazard

Table 1

Fire hazardous category B should include premises in the technological process of which flammable materials are located and handled, while the level of fire danger is taken into account by introducing such a criterion as fire load and is established by a differentiated classification, according to which premises of category B are divided into four categories (B1, B2 , B3, B4) depending on the specific temporary fire load (indoors) (Table 4).

1.2. Characteristics of categories B1–B4 premises

Determination of the fire hazardous category of a room is carried out by comparing the maximum value of the specific temporary fire load (hereinafter referred to as the fire load) in any of the areas with the value of the specific fire load given in Table. 4.

Table 4

At the same time, categories B1, B2 and B3 in terms of fire protection requirements basically correspond to category B currently in force in building codes, and category B4, from a practical point of view, is similar to the existing category D (with a small fire load).

When designing production, warehouse and agricultural premises and buildings, one should be guided by the following provisions when assigning fire safety measures specified in the current standards:

For premises of categories B1, B2, B3, the requirements established by the current SNiP for category B should be applied. At the same time, for premises of category B1, it is necessary to establish more stringent requirements (20%) for the standardized parameters of escape routes and the area of ​​such premises (if this area is established by the standards ).

For premises of category B3, in justified cases, it is allowed to make the specified requirements less stringent (by 20%) compared to the current requirements for category B;

in premises classified in accordance with approved safety regulations as category D (where only non-flammable substances and materials are used in the technology and in a cold state), the areas and parameters of escape routes are not standardized;

One of the most important functions of state authorities, local governments, organizations, peasant or farm enterprises and other legal entities, regardless of their organizational, legal forms and forms of ownership, is to ensure fire safety. This is stated in the legislation of the Russian Federation.

Let's look at the categories

“A” fire and explosion hazard: the presence in buildings of flammable gases and flammable liquids in such quantities that it becomes possible to form steam-gas mixtures, the ignition of which develops a calculated excess explosion pressure exceeding 5 kPa. The flash point of such gases and liquids is no more than 28° C.

An official document showing to what extent the object under study complies with (FS), what measures have been taken for this and how high it is, is called the fire safety declaration of the object.

“B” fire and explosion hazard: the presence in the premises of flammable dust or fibers, flammable liquids, the flash point of which is more than 28 ° C. The presence in the premises of flammable liquids in such quantities that the formation of explosive dust-air and steam-air mixtures is possible, the ignition of which develops the calculated excess explosion pressure , exceeding 5 kPa.

“B1” – “B4” are fire hazardous. This category includes rooms in which flammable and low-flammable liquids, solid flammable and low-flammable substances and materials, substances and materials in the room when interacting with water, air oxygen or with each other tend to burn, provided that the rooms in which they are in stock or in circulation and do not belong to categories A or B.

“G” – moderate fire hazard. Premises containing non-combustible substances and materials, the state of which is defined as hot, incandescent or molten. During their processing, radiant heat, sparks and flames are released. Category “G” also includes rooms where flammable gases, liquids and solids that are fuel are located.

“D” reduced fire hazard – these are rooms in which non-combustible substances and materials are in a cold state.

Categories of premises in terms of explosion and fire hazards are determined at the design stage of various structures and buildings and comply with these standards and departmental technological design standards, approved in the prescribed manner.

Categories of premises according to explosion and fire hazard

Notes

1 Division of premises into categories B1-B4 carried out in accordance with subsection 5.3 of this technical code.

• flammable and low-flammability liquids with a flash point of 120 °C and higher in lubrication, cooling and hydraulic drive systems of equipment weighing less than 60 kg per piece of equipment with a system pressure of less than 0.2 MPa, while the distance between equipment is not standardized;
• low-flammability substances and materials, building materials of flammability group G1 as a temporary fire load. The mass of low-flammability substances and materials, building materials of flammability group G1 is not limited, provided that there are no other flammable substances and materials in the room. If there are flammable substances and materials in the room, the calculation is made taking into account the total mass of low-flammability substances and materials, building materials of flammability group G1;
• electrical cables for powering technological and engineering equipment, lighting devices (except for oil-filled ones), while this provision does not apply to server rooms, automatic telephone exchanges and the like;
• GG (provided that they are available or in circulation, according to the calculation they do not belong to category A and there is no other fire load);
• non-flammable cargo in flammable packaging, with:
• packaging means (pallets, backing sheet, etc.) according to GOST 21391 do not belong to flammable packaging and, if they contain flammable substances and materials, are taken into account as a temporary fire load;
• flammable packaging whose weight exceeds 20% of the weight of non-flammable cargo is taken into account as a temporary fire load;
• flammable bedding on the floor for keeping animals, birds and beasts in livestock farms; poultry and fur farming buildings, provided that the specific fire load does not exceed 100 MJ/m2 (regardless of the total fire load).

• pieces of furniture in workplaces;
• rooms with wet processes (refrigerators and cold rooms with non-flammable refrigerant, washing rooms and similar buildings), and the temperature in refrigerators and cold rooms should not exceed 0 ° C.

To carry out all fire safety measures, it is important to assess the premises. After all, the occurrence and speed of fire spread directly depends on the flammability of the materials located in the buildings, as well as on the technological nuances of production at the facilities.

Main classification

Depending on the materials, liquids or gases in buildings, there are 5 degrees of danger. At the same time, categories of premises are also assessed separately. When dividing them according to the degree of danger, the presence of flammable substances in them and their quantity are taken into account. The characteristics of technological processes that take place in these premises also play an important role.

The fire hazardous properties of materials are determined as a result of research and calculations according to established rules, depending on the surrounding parameters.

Category A

The greatest attention is paid to structures and premises that are assigned a class of increased explosion and fire hazard. It depends on the substances and materials inside.

Thus, category A is assigned to those rooms containing flammable liquids and combustible gases. Moreover, their flash point is no more than 28 o C. To assign this category of premises for fire hazard, it is necessary that the specified substances are stored there in quantities that will be sufficient to form explosive air-steam mixtures. When they ignite, an excess pressure exceeding 5 kPa should develop.

Also, this category is assigned if there are materials or other substances in the room that can burn or explode even when interacting with oxygen from the air, water, or each other. In this case, the excess pressure created must exceed 5 kPa.

Examples of class A premises

The easiest way to understand exactly how the danger category of a premises is determined is by considering which structures are classified as class A. Thus, this group includes:

• warehouses where fuels and lubricants, gasoline and containers intended to contain them are stored;
• stations designed for the production, storage, processing, pumping and spilling of flammable liquids (flammable liquids);
• points for processing and washing flammable liquid containers;
• acetylene and hydrogen stations;
• stationary alkaline and acid battery installations;
• storerooms and paint shops that use solvents, varnishes, nitro paints and other flammable liquids, the flash point of vapors in which is less than 28 o C.

Professionals should know which substances fall into this category. Thus, these include acetylene, hydrogen, natural gas, vapors of nitro solvents and gasoline.

Class B danger

But these are not all categories of premises that are considered fire hazardous. True, you need to understand that class A buildings are those buildings that belong to the group of increased explosion hazard. The next group is less scary.

Category B premises include those in which flammable liquids with a flash point above 28 o C, flammable liquids, fibers and dust are stored. In this case, the condition must be met that their quantity is sufficient so that upon ignition the design pressure exceeds 5 kPa.

Examples of category B premises

There is a fairly large list of buildings and structures that can safely be classified as class B. The specified fire category of the premises can be assigned:

• workshops where coal dust, powdered sugar, and wood flour are prepared and transported;
• production of hay flour, grinding and beating areas of mills, grist mills;
• workshops that specialize in painting work and use paints, varnishes with a flash point of more than 28 o C, and places where they are stored;
• diesel fuel warehouses, pumping stations, drain racks for its pumping;
• ammonia refrigeration units;
• fuel oil facilities of boiler houses and power plants;
• industries involved in the production of fiberglass and plastic products.

Also, category B can be assigned to those rooms in which parts are washed and wiped using kerosene or gasoline. It also includes washing stations where they clean tanks containing diesel fuel, fuel oil and other substances whose flash point is more than 28 o C.

Class B buildings

The following categories of premises in terms of fire danger are no longer so scary. Thus, other requirements are put forward for buildings, warehouses and other structures that belong to class B. These premises include those containing flammable or slow-burning materials, substances, and liquids. They are capable of burning only when interacting with air, water, or each other, but do not belong to categories A or B.

For each room, a subgroup within B1-B4 can also be allocated. It is determined depending on the location of the fire hazard load and its concentration.

Examples of class B premises

Buildings and structures of category B may include the following:

• carpentry, sawmills, woodworking or combined workshops;
• peat warehouses, coal overpasses, closed storage areas for coal, fuel and lubricants, with the exception of gasoline;
• grain cleaning areas of mills, feed kitchens;
• workshops where primary dry processing of cotton and flax is carried out;
• textile, clothing factories, paper industry workshops;
• warehouses for oil paints and varnishes, diesel fuel;
• fuel oil and lubrication facilities of factories;
• car garages;
• libraries, archives, dressing rooms;
• bitumen and asphalt plants;
• transformer substations.

It is important to understand that the same structure can be classified into different hazard classes. This is due to the fact that the category of premises is determined based on what the maximum possible concentration of hazardous substances may be. The calculation is made for each specific condition individually.

Category G, D

The safest premises are those that belong to the last two groups. In buildings of category G there may be non-combustible materials and substances in a red-hot, molten or simply hot state, as well as solids, liquids or flammable gases. The process of processing them may be accompanied by the release of heat, flames or sparks; they are used as fuel.

Examples of buildings of class G and D

The safest premises are categories G and D. Experts include the following in the first group:

• metal stamping and hot rolling workshops;
• firing shops located in brick, lime, and cement factories;
• forges, boiler rooms, engine departments of diesel power plants;
• welding, smelting, foundry, forging shops;
• departments specializing in the repair of internal combustion engines.

• metal cold rolling departments;
• irrigation pumping, blowing, compressor stations;
• meat, fish, dairy and meat products processing shops;
• greenhouses, with the exception of those heated by gas.

Determination of building categories A and B

Before assigning a certain hazard class, specialists inspect all premises. Based on the summed volume of areas and the categories assigned to them, it is determined which group the entire building belongs to. The calculation is carried out based on certain standards.

So, for example, class A will be assigned if premises of category A occupy more than 5% of the total area or 200 m 2. If their total number does not exceed 25% (but not more than 1000 m2) and they are equipped with automatic fire extinguishing installations, then the building will not be classified as group A.

If premises safety categories have been established and it is determined that more than 5% of the total area or 200 m2 belongs to classes A and B in a building, then it can be assigned group B. However, this is possible if it cannot be classified as category A. The situation is different in cases where the premises are equipped with automatic fire extinguishing systems. Class B will not be assigned if the summed areas belonging to categories A and B do not exceed 25% or 1000 m2.

Buildings belonging to hazard classes B, D, D

It is not enough to know how the category of premises is determined. In most cases, it is important to assign a fire hazard class to the entire building. So, if the total area of ​​premises classified as categories A, B, B1, B2, B3 is more than 5% (or more than 10% if there are no areas classified as groups A and B), then the structure will be classified as class B. But this is only possible if it does not belong to category A or B. However, the building will not be classified as group B if the number of specified areas is no more than 25% or 3500 m2 and it is equipped with automatic fire extinguishing installations.

If it has been determined that in a building the categories of premises in terms of explosion and fire hazard are divided between groups A, B, B1-B3, D, and their total number exceeds 5% of the total area, then it can be classified as class D. If the structure is equipped with automatic extinguishing devices fires, then it will not be classified as group D, provided that the total area of ​​premises A, B, B1-C3, D is no more than 25% or 5000 m2.

Method of determination

In order to find out how dangerous a building is, it is important to understand what categories of premises in it predominate in terms of explosion and fire hazard. To begin with, select and justify the required design option. It is determined using a certain method. The calculation is based on the fact that in the event of an emergency, the most dangerous option will develop.

It is important to determine the amount of substances that form explosive mixtures that can enter the room. Experts carry out calculations for situations when:

• an accident occurs in one of the devices;
• all contents of the device exit into the room;
• there is a leak from the pipelines that supply the device for the period necessary to turn them off;
• evaporation of the liquid begins from the surfaces on which it was spilled, which were freshly painted, and from containers.

In order to correctly determine the fire category of a room, it is necessary to take into account not only the possible amount of flammable air mixtures, but also the free volume of the room. It is defined as the difference between its total capacity and the space occupied by all the technological equipment located there. If it is impossible to calculate it, then it is considered to be 80% of the total volume.

After selecting the required design option, the possible excess pressure is directly determined. For flammable substances, gases, and flammable liquids, special formulas are used. Categories of premises are determined based on which atoms of flammable substances will be in the room. In this case, the possible maximum value is taken as the calculated temperature. The mass of flammable gases, liquids, their combustion coefficient, initial and maximum possible pressure are also taken into account. The formula also includes the volume of the room.

Classification of residential buildings

As a rule, the calculation of fire safety categories of premises is performed for warehouses, workshops, production facilities and other industrial facilities. It is not used for residential properties. This is due to the fact that, as a rule, they do not store explosive substances, flammable liquids and materials.

But it will not hurt to know that the category of residential premises can be determined by electrical safety. This also affects the likelihood of fires. For example, in rooms with high humidity there may be problems when using unprotected electrical appliances and their control devices. Thus, dangerous areas include kitchens, verandas, vestibules, attics, attics of heated houses, sheds, sheds, cellars, greenhouses, greenhouses.