When constructing any building, the issues of organizing emergency exits and evacuation routes in the construction must be considered even at the project stage. in case of emergency, location of funds But these points can be considered only if you know the degree of fire resistance of the building. Difficulties may arise with this at present, since most often the same type of structures are erected in cities. But next we will try to understand how fire resistance is determined and what it depends on.
What is fire resistance?
This is the ability of structures and individual designs withstand the onslaught of fire without destruction or deformation. It is the degree of fire resistance of the building that will determine how quickly the fire can spread throughout the structure if a fire breaks out.
All indicators are determined taking into account SNiP. These standards make it possible to determine the level of not only the building, but also all the materials that were used during construction.
Classification by flammability
- Fireproof.
- Resistant to fire. They can be made of combustible materials, but which have a special treatment or coating on top. An example is wooden door, lined with steel or covered with asbestos.
- Combustible. They have a low ignition temperature and burn quickly when exposed to fire.
Basis for determining fire resistance
The determining basis for determining the degree of fire resistance of a building is the time that has passed from the moment of the fire to the appearance of the first noticeable defects. These include:
- Cracks and damage to the integrity of the surface, which can facilitate the penetration of flame or combustion products.
- Increasing the temperature of materials by more than 160 degrees.
- Deformation load-bearing structures and main components, which causes the collapse of the entire structure.
Buildings built from wooden structures have a low degree of fire resistance; reinforced concrete ones are considered the safest in terms of fire, especially if they contain cement with high level fire resistance.
Dependence of fire resistance on materials
The ability of a building to withstand fire largely depends on the materials from which it is built. They can be classified based on the following characteristics:
The degree of fire resistance of building structures depends on the time required for the material to deform:
- Ceramic or silicate bricks begin to deform 300 minutes after the start of the fire.
- Concrete floors, more than 25 cm thick, after two hours.
- It takes 75 minutes for plaster-coated timber structures to begin to deform.
- An hour will pass before the door treated with fire retardant begins to deform.
- 20 minutes of exposure to fire is sufficient.
Fire resistance degree brick buildings quite high, which cannot be said about metal ones, which already at 1000 degrees turn into a liquid state.
Assignment of fire safety category
According to regulatory requirements, only after the structure has been assigned a certain fire safety category can the degree of fire resistance of the building be determined. And this is done based on the following signs:
- Based on changes in thermal insulation performance when compared with the state before the fire.
- According to the barrier effect, which eliminates the formation of cracks in structures.
- By reducing the ability to perform load-bearing functions.
When determining the degree of fire resistance of a building, the area of the structure and the quality of all materials used must be taken into account.
Characteristics of degrees of fire resistance
Their determination is made on the basis of SNiP; the fire resistance of the main functional structures is always taken as a basis. Let's consider how many degrees of fire resistance of buildings and structures exist and what are their main characteristics:
Types of fire resistance
Special Requirements The ability to withstand fire is required of all building structures. The following indicators are important for them:
- Ability to perform a load-bearing function.
- Thermal insulation.
- Integrity.
The safety of the building also plays an important role. Experts today divide the fire resistance of structures into two types:
- Factual.
- Required.
The actual degree of fire resistance of a building is the ability to withstand fire, which was determined during the examination. Available regulatory documents are taken as criteria for evaluation. For designs different types fire resistance limits have already been developed. This data is very easy to find and use for your work.
Required fire resistance is the indicators that a building must have in order to comply with all fire safety standards. They are determined regulatory documents and depend on many structural characteristics:
- total area building.
- Number of floors.
- Purpose.
- Availability of means and installations for extinguishing fires.
If during the inspection it turns out that the actual degree of fire resistance of buildings and structures is equal to or exceeds the required one, then the structure complies with all standards.
Fire hazard classes
To determine the fire resistance of the entire building, structures are divided into several categories, and buildings into several classes.
- KO - non-fire hazardous. There are no materials in the premises that quickly ignite, and the main structures are not characterized by spontaneous combustion and combustion at temperatures close to 500 degrees.
- K1 - low fire danger. Minor damage may be allowed, but not more than 40 cm. There is no combustion, no thermal effect occurs.
- K2 - moderate fire danger. Damage can reach 80 cm, but there is no thermal effect.
- K3 - fire hazard. Integrity violations of more than 80 cm, there is a thermal effect and fire is possible.
- CO. All utility rooms, main structures and staircases with openings correspond to class KO.
- C1. There may be minor damage to leading structures up to K1, and external ones up to K2. Stairs and openings must be in excellent condition.
- C2. Damage to main structures can reach K2, external K3, and stairs up to K1.
- C3. Stairs with openings are damaged up to K1, and everything else is not taken into account.
Rules for determining the resistance of a building to fire
It is not enough to know about the importance of fire resistance of buildings and structures; it is also important to be able to determine it. And for this there are some rules:
1. Testing a building requires having a plan at hand, and you will also need:
- Code of Practice for Fire Resistance reinforced concrete structures.
- Guidelines for Determining Fire Resistance Limits.
- Manual for SNiP “Preventing the spread of fire.”
2. The fire resistance limit is determined by the time the structure is exposed to fire. When the structures reach one of the limits, the fire is stopped.
3. Before starting testing, you need to study the documentation for the building, which contains information about the materials and their approximate fire resistance.
4. It is necessary to pay attention in the documents to the existing conclusion on the application special technologies to improve fire safety.
5. A preliminary study of the building also involves consideration of all utility rooms, stairs and stairwells, attic compartments. They may be constructed from other materials or may have visible damage at the time of testing.
6. Modern architecture very often used in construction Newest technologies, which may affect strength and fire resistance. These points also need to be taken into account.
7. Before carrying out the fire resistance determination, it is necessary to prepare extinguishing agents, check the serviceability of the hoses, and call the fire brigade.
When all preliminary measures have been carried out, you can proceed directly to the practical determination of fire resistance.
Practical definition of fire resistance
When starting the practical part, it is important to take the architect's plan with you, even if it has been carefully studied. The next steps are:
An indicator of the fire resistance of a material will be the time of exposure to fire and the speed of its spread. U different buildings this figure can vary from 20 minutes to 2.5 hours. The combustion speed is even less - from instantaneous to 40 cm per minute.
This is how the fire resistance of a building is calculated in practice.
Ways to increase fire resistance
It is not always possible to use only non-flammable or low-flammable materials during construction, so ways to increase their resistance to fire come to the rescue.
The most commonly used are the following:
If multi-component chemicals to increase fire resistance, it must be taken into account that some of them contain organic substances that decompose at temperatures above 300 degrees, releasing toxic substances. Therefore, it is better to give preference to mineral-based coatings with liquid glass.
It is not difficult to determine the fire resistance of buildings and structures. It is important to carry out everything preliminary preparations and we can consider that most of the work is done. The calculation can be considered more costly than complex. The most important thing is to be especially careful during testing and control the temperature in the oven.
The approach to the construction of any buildings and structures should be based on safety from different points of view. And not the least important place here is fire safety. The resistance of the structure to fire depends on emergency situations human lives.
Fires caused by humans have become quite common and widespread. Thousands of fires occur every year, causing a range of unpleasant consequences. Therefore, during the construction of structures great importance has a fire resistance rating for the building. Each constructed object is assigned a specific fire resistance number, according to the existing classification. Next, we will consider the classification in more detail and describe the parameters of each class.
What is the degree of fire resistance?
| Fire resistance level of the structure | Fire safety class of the structure | Maximum permissible height structures, cm | Allowable floor S, cm2 |
| I | Co Co Cl | 7500 5000 2800 | 250000 250000 220000 |
| II | Co Co Cl | 2800 2800 1500 | 180000 180000 180000 |
| III | Co Cl C2 | 500 500 200 | 10000 80000 120000 |
| IV | Without rationing | 500 | 50000 |
| V | Without rationing |
SNiP 31-01-03
This definition is understood as the ability of structures to restrain the expansion of the flammable area without the building losing its ability to further operate. The list of these properties consists of enclosing and load-bearing abilities.
If the structure loses bearing capacity- it will certainly collapse. It is by destruction that this definition is meant. As for the barrier ability, its loss is considered to be the level of heating of materials until cracks or holes form through which combustion products can spread into adjoining rooms or heating to the temperature at which the combustion process of the material begins.
The indicator of the maximum degree of fire resistance of structures is the time interval from the moment of fire formation to the appearance of signs of such losses (measured in hours). To test the performance of materials under fire conditions, a prototype is taken and placed in equipment for such experiments - a special furnace. In a kiln environment, the test item is subjected to high-temperature fire, which places stress on the material that is specific to the specific project.
The degree of fire resistance, when determining its limit, also depends on the ability to increase the temperature at individual points or the average value of the increase in temperature indicators over the surface, which is compared with the original one. The structural elements of the structure made of metal have the minimum resistance to fire, and the maximum resistance is reinforced concrete, in the manufacture of which cement with high fire resistance characteristics was used. The maximum fire resistance level can reach 2.5 hours.
Also, when determining the ability of a structure to withstand fire, the limit of fire spread is taken into account. It is equivalent to the extent of damage in areas that were outside the combustion zone. This figure can be 0-40 cm.
We can safely say that the degree of fire resistance of structures directly depends on the ability of the materials used in its construction to withstand high temperatures am, affecting the surface in a fire environment.
According to the degree of combustion, materials are divided into 3 groups:
- Fireproof (reinforced concrete structures, brick, stone elements).
- Refractory (materials from the combustible group, the fire resistance of which is increased by treatment with special means).
- Combustible (quickly ignites and burns well).
To classify materials, a special set of documents is used - SNIP.
How is it determined?
The degree of fire resistance is a representative of the most significant parameters of a structure, not inferior in importance to the design features in terms of fire safety and functional characteristics. But what should you pay attention to in order to determine it with utmost accuracy? To do this, you need to consider the following construction parameters:
- Number of storeys.
- Actual area of the structure.
- Nature of the building's purpose: industrial, residential, commercial, etc.
To determine the degree of fire resistance (I, II, etc.) it is necessary to determine exclusively the regulatory documents and those given in SNIP. Also, for such purposes and the design of high-rise buildings, DBN 1.1-7-2002 is used, to determine the fire safety of multi-story structures, 4 DBN V.2.2-15-2005 are used, and to familiarize yourself with the fire safety requirements for structures with a large number of floors, 9 DBN V.2.2 are used -24:2009. Only the use of special documentation will allow you to obtain the most full information about the degrees of fire resistance of buildings with different design features.
Similar questions have arisen repeatedly. I keep an extract from the Soviet norms
IIIa from SNiP 2.01.02-85* APPENDIX 2 Reference
SAMPLE CONSTRUCTION CHARACTERISTICS OF BUILDINGS
DEPENDING ON THEIR DEGREE OF FIRE RESISTANCE
1. Fire resistance level
2. Design characteristics
I
Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials
II
Same. In the coatings of buildings it is allowed to use unprotected steel structures
III
Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete. For floors, it is allowed to use wooden structures protected by plaster or low-flammability sheet and slab materials. There are no requirements for fire resistance limits and fire spread limits for coating elements, while attic wood roofing elements are subject to fire retardant treatment
IIIa
Buildings predominantly with frame design diagram. The frame elements are made of unprotected steel structures. Enclosing structures - made of profiled steel sheets or other non-combustible sheet materials with low-flammability insulation
IIIb
The buildings are predominantly one-story with a frame structural design. Frame elements are made of solid or laminated wood, subjected to fire retardant treatment, ensuring the required limit of fire spread. Enclosing structures - made of panels or element-by-element assembly, made using wood or wood-based materials. Wood and other combustible materials of enclosing structures must be subjected to fire retardant treatment or protected from exposure to fire and high temperatures in such a way as to ensure the required limit of fire spread.
IV
Buildings with load-bearing and enclosing structures made of solid or laminated wood and other combustible or low-combustible materials, protected from fire and high temperatures by plaster or other sheet or slab materials. There are no requirements for fire resistance limits and fire spread limits for coating elements, while attic wood roofing elements are subject to fire retardant treatment
IVа
The buildings are predominantly one-story with a frame structural design. The frame elements are made of unprotected steel structures. Enclosing structures - made of profiled steel sheets or other non-combustible materials with combustible insulation
V
Buildings, the load-bearing and enclosing structures of which are not subject to requirements for fire resistance limits and fire spread limits
Note. The building structures given in this appendix must meet the requirements of Table. 1 and other standards of this SNiP.
The highest degree of fire resistance is I (mausoleum).
Fire resistance degree
fire resistance limit
Structural collapse;
Fire resistance limits:
— silicate brick — ~5 h
Table 3
| Fire resistance degree | |
| I | |
| II | The same. It is allowed to use unprotected steel structures in building coverings |
| III | |
| III a | |
| III b | |
| IV | |
| IV a | |
| V |
— impregnation with fire retardants;
- cladding;
- plaster.
- borax Na 2 B 4 O 7 * 10H 2 O.
asbestos cement sheets;
Related information:
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All about fire safety 0-1.ru
| Topic qualifier: | ||
| last | There are 0 comments in the discussion | |
| We need the help of specialists in determining the degree of fire resistance of a building! 3-storey building, wooden structures attic, metal roofing. The walls are brick plastered. The interfloor ceilings are reinforced concrete, including the attic. Wooden structures treated with a fire retardant compound. A controversial question arises: what degree of fire resistance of a building is 2 or 3. In accordance with table. 21 FZ-123 and a guide to determining degrees of fire resistance, it turns out that the building is of the second degree of fire resistance, but the attic is confusing. The inspector claims that 3 is only due to wooden attic. I don't agree (maybe I'm wrong). A reasoned answer would be desirable. |
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| 5.4.5. The fire resistance limits and fire hazard classes of attic covering structures in buildings of all degrees of fire resistance are not standardized, and the roofing, rafters and sheathing, as well as the lining of eaves overhangs, may be made of combustible materials, except in specially specified cases. Gable structures may be designed with non-standardized fire resistance limits, while the gables must have a fire hazard class corresponding to the fire hazard class of external walls with outside. Information on structures related to elements of attic coverings is given design organization V technical documentation on the building. In buildings of I - IV degrees of fire resistance with attic coverings, with rafters and (or) sheathing made of combustible materials, the roof should be made of non-combustible materials, and the rafters and the sheathing in buildings of fire resistance class I should be treated fire retardant compounds I group of fire retardant efficiency, in buildings of II - IV degrees of fire resistance with fire retardant compounds not lower than group II of fire retardant efficiency according to GOST 53292, or carry out their structural fire protection, which does not contribute to the hidden spread of combustion. In buildings of classes C0, C1, the structures of cornices, lining of eaves overhangs of attic coverings should be made of materials NG, G1, or these elements should be sheathed with sheet materials of a flammability group of at least G1. For these structures, the use of flammable insulation is not allowed (with the exception of vapor barriers up to 2 mm thick), and they should not contribute to the hidden spread of combustion. |
||
| Yakhont ® why are you considering the attic to determine the fire resistance limit of a building? An attic is not a floor (see the term building and the term attic), and rooms can only be placed on a floor. You need to consider the building down to the attic. And such structures as you described (brick walls, interfloor ceilings reinforced concrete, including attics), as a rule give II degree. | ||
| II CO | ||
| II degree C0. The inspector is wrong. The topic of walls, flights and landings in the staircase, by the way, has not been disclosed. Maybe this is where the reason for the doubts about the third degree lies. |
||
| Handsome inspector! The degree of fire resistance of a building can be determined by eye! Actually, the degree of fire resistance is included in the project)) | ||
| Construction norms and rules SNiP 2.01.02-85* "Fire safety standards" Appendix 2, these standards reveal how they are mainly distributed degree of fire resistance, and how can they be identified. They are ancient, but very understandable. The stairs and flights are not indicated in them. According to your description, it is undoubtedly II degree. The inspector is wrong. |
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| Thanks to everyone who responded! | ||
| Discussion closed | ||
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The conditions for the development of fire in buildings and structures are largely determined by the degree of their fire resistance. Fire resistance degree is the ability of a building (structure) as a whole to resist destruction in a fire. Buildings and structures are divided into five degrees according to the degree of fire resistance (I, II, III, IV, V). The degree of fire resistance of a building (structure) depends on the flammability and fire resistance of the main building structures and from the limits of fire spread on these structures.
Based on flammability, building structures are divided into fireproof, non-combustible and combustible. Fireproof are building structures made of fireproof materials. Non-combustible structures are considered to be those made of non-combustible materials or of combustible materials protected from fire and high temperatures by non-combustible materials (for example, fire door, made of wood and covered with asbestos sheets and roofing steel).
The fire resistance of building structures is characterized by their fire resistance limit, which is understood as the time in hours after which 1 of 3 signs occurs during a fire:
1. Structural collapse;
2. Formation of through cracks or holes in the structure. (Combustion products penetrate into adjacent rooms);
3. Warming up the structure to temperatures that cause spontaneous combustion of substances in adjacent rooms (140-220 o).
Fire resistance limits:
- ceramic brick - 5 hours (25 cm-5.5; 38-11 hours)
— silicate brick — ~5 h
- concrete 25 cm thick - 4 hours (the cause of destruction is the presence of up to 8% water);
- wood covered with gypsum 2 cm thick (total 25 cm) 1 hour 15 minutes;
— metal constructions- 20 min (1100-1200 o C-metal becomes plastic);
- entrance door treated with fire retardant - 1 hour.
Porous concrete, hollow brick have great fire resistance.
Unprotected metal structures have the lowest fire resistance limit, and reinforced concrete ones have the highest.
According to DBN 1.1.7-2002 “Fire protection. Fire safety construction projects", all buildings and structures are divided according to fire resistance into eight degrees (see table.
Table 3
Fire resistance of buildings and structures
| Fire resistance degree | Design characteristics |
| I | Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials |
| II | |
| III | Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete For floors, it is allowed to use wooden structures protected by plaster or low-flammable sheet and slab materials. Requirements regarding fire resistance limits and fire spread limits are not established for coating elements, while elements of attic coverings made of wood can be treated with fire retardant treatment |
| III a | Buildings predominantly with a frame structural design Frame elements - from unprotected steel structures Enclosing structures - from steel profiled sheets or other non-combustible sheet materials with low-combustible insulation |
| III b | The buildings are predominantly one-story with a frame structural design. Frame elements are made of solid or laminated wood, subjected to fire retardant treatment, which provides the necessary limit for the spread of fire. Enclosing structures are made of panels or element-by-element assembly, made using wood or materials based on it. Wood and other combustible materials. enclosing structures must be subjected to fire retardant treatment or protected from the influence of fire and high temperatures in such a way as to ensure the desired limit of fire spread |
| IV | Buildings with load-bearing and enclosing structures made of solid or laminated wood and other combustible and low-combustible materials, protected from the influence of fire and high temperatures by plaster and other sheet and slab materials. Coating elements are not subject to requirements regarding fire resistance limits and flame propagation limits, while the elements attic floors made of wood can be treated with fire retardant treatment |
| IV a | The buildings are predominantly one-story with a frame structural design. Frame elements are made of unprotected steel structures. Enclosing structures are made of steel profiled sheets or other non-combustible materials with combustible insulation. |
| V | Buildings, the load-bearing and enclosing structures of which are not subject to requirements regarding fire resistance limits and fire spread limits |
Protection of wooden structures from fire:
To protect wooden structures from fire, use:
— impregnation with fire retardants;
- cladding;
- plaster.
Fire retardants — chemical substances, intended to impart non-flammability properties to wood (French physicist Gay-Lussac. 1820 Ammonium salts).
Fire retardants - reduce the rate of release of gaseous products, reduce the yield of resin as a result of chemical interaction with cellulose.
For wood impregnation the following is used:
- ammonium phosphate (NH 4) 2 HPO 4
- ammonium sulfate (NH 4) 2 SO4
- borax Na 2 B 4 O 7 * 10H 2 O.
Deep impregnation is carried out in autoclaves at a pressure of 10-15 atm for 2-20 hours.
Soaking is carried out in a fire retardant solution at a temperature of 90 o C for 24 hours.
Impregnation with fire retardants transforms wood into the category of difficult-to-burn materials. Surface treatment prevents wood from burning within a few minutes.
Cladding and plaster - protect wooden structures from fire (slow heating).
Wet plaster— fire protection 15-20 min.
Facing materials: gypsum plaster(fire protection 10 min);
asbestos cement sheets;
Related information:
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Fire resistance of buildings and structures
The conditions for the development of fire in buildings and structures are largely determined by the degree of their fire resistance.
Fire resistance degree is the ability of a building (structure) as a whole to resist destruction in a fire. Buildings and structures are divided into five degrees according to the degree of fire resistance (I, II, III, IV, V). The degree of fire resistance of a building (structure) depends on the flammability and fire resistance of the main building structures and on the limits of fire spread through these structures.
Based on flammability, building structures are divided into fireproof, non-combustible and combustible. Fireproof are building structures made of fireproof materials. Non-combustible structures are considered to be structures made of materials that do not burn easily or of combustible materials protected from fire and high temperatures by non-combustible materials (for example, a fire door made of wood and covered with sheet asbestos and roofing steel).
The fire resistance of building structures is characterized by their fire resistance limit, which is understood as the time in hours after which 1 of 3 signs occurs during a fire:
1. Structural collapse;
2. Formation of through cracks or holes in the structure. (Combustion products penetrate into adjacent rooms);
3. Warming up the structure to temperatures that cause spontaneous combustion of substances in adjacent rooms (140-220 o).
Fire resistance limits:
- ceramic brick - 5 hours (25 cm-5.5; 38-11 hours)
— silicate brick — ~5 h
- concrete 25 cm thick - 4 hours (the cause of destruction is the presence of up to 8% water);
- wood covered with gypsum 2 cm thick (total 25 cm) 1 hour 15 minutes;
- metal structures - 20 minutes (1100-1200 o C-metal becomes plastic);
- entrance door treated with fire retardant - 1 hour.
Porous concrete and hollow bricks have greater fire resistance.
Unprotected metal structures have the lowest fire resistance limit, and reinforced concrete ones have the highest.
According to DBN 1.1.7-2002 “Fire protection. Fire safety of construction projects,” all buildings and structures are divided into eight degrees according to fire resistance (see Table 3).
Table 3
Fire resistance of buildings and structures
| Fire resistance degree | Design characteristics |
| I | Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials |
| II | The same. It is allowed to use unprotected steel structures in building coverings |
| III | Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete For floors, it is allowed to use wooden structures protected by plaster or low-flammable sheet and slab materials. Requirements regarding fire resistance limits and fire spread limits are not established for coating elements, while elements of attic coverings made of wood can be treated with fire retardant treatment |
| III a | Buildings predominantly with a frame structural design Frame elements - from unprotected steel structures Enclosing structures - from steel profiled sheets or other non-combustible sheet materials with low-combustible insulation |
| III b | The buildings are predominantly one-story with a frame structural design. Frame elements are made of solid or laminated wood, subjected to fire retardant treatment, which provides the necessary limit for the spread of fire. Enclosing structures are made of panels or element-by-element assembly, made using wood or materials based on it. Wood and other combustible materials. enclosing structures must be subjected to fire retardant treatment or protected from the influence of fire and high temperatures in such a way as to ensure the desired limit of fire spread |
| IV | Buildings with load-bearing and enclosing structures made of solid or laminated wood and other combustible and low-combustible materials, protected from the influence of fire and high temperatures by plaster and other sheet and slab materials. Coating elements are not subject to requirements regarding fire resistance limits and flame propagation limits, while attic elements Wood floors can be treated with fire retardant treatment |
| IV a | The buildings are predominantly one-story with a frame structural design. Frame elements are made of unprotected steel structures. Enclosing structures are made of steel profiled sheets or other non-combustible materials with combustible insulation. |
| V | Buildings, the load-bearing and enclosing structures of which are not subject to requirements regarding fire resistance limits and fire spread limits |
Protection of wooden structures from fire:
To protect wooden structures from fire, use:
— impregnation with fire retardants;
- cladding;
- plaster.
Fire retardants are chemical substances designed to give wood non-flammable properties (French physicist Gay-Lussac. 1820 Ammonium salts).
Fire retardants - reduce the rate of release of gaseous products, reduce the yield of resin as a result of chemical interaction with cellulose.
For wood impregnation the following is used:
- ammonium phosphate (NH 4) 2 HPO 4
- ammonium sulfate (NH 4) 2 SO4
- borax Na 2 B 4 O 7 * 10H 2 O.
Deep impregnation is carried out in autoclaves at a pressure of 10-15 atm for 2-20 hours.
Soaking is carried out in a fire retardant solution at a temperature of 90 o C for 24 hours.
Impregnation with fire retardants transforms wood into the category of difficult-to-burn materials. Surface treatment prevents wood from burning within a few minutes.
Cladding and plaster - protect wooden structures from fire (slow heating).
Wet plaster - fire protection 15-20 min.
Facing materials: gypsum plaster (fire protection 10 min);
asbestos cement sheets;
Related information:
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How to determine the actual fire resistance limit and fire hazard class of a building structure?
Question:
Is it possible to use wooden structures as load-bearing roof structures in a school building? The building has fire resistance degree II, functional fire hazard class F1.1.
Answer:
In accordance with Article 36 Federal Law dated July 22, 2008 N 123-FZ " Technical regulations on fire safety requirements" (as amended on June 23, 2014), building structures based on fire hazard are divided into the following classes:
1) non-fire hazardous (K0);
2) low fire hazard (K1);
3) moderate fire hazard (K2);
4) fire hazardous (K3).
Currently, when determining the actual fire hazard classes of building structures, the following is used:
— GOST 30403-2012 “Building structures.
Test method for fire hazard."
Currently, when determining the actual fire resistance limits of structures, the following are used:
— GOST 30247.0-94 “Building structures. Test methods for fire resistance. General requirements»;
— GOST 30247.1-94 “Building structures. Test methods for fire resistance. Load-bearing and enclosing structures."
Based on the results of fire tests, test reports are drawn up (clause 12 GOST 30247.0-94, clause 10 GOST 30247.1-94, clause 11 GOST 30403-2012), which indicate the relevant data, including the actual fire resistance limits of building structures and actual fire hazard classes of building structures.
Accordingly, to determine the actual fire resistance limits and fire hazard classes of building structures, it is necessary to conduct fire tests in an accredited testing laboratory.
Based on information only about the material from which the building structure is made, it is impossible to determine the actual fire resistance limit and fire hazard class of the building structure.
In accordance with Part 10 of Article 87 of the Federal Law of July 22, 2008 N 123-FZ, fire resistance limits and fire hazard classes of building structures similar in shape, materials, design building structures that have passed fire tests can be determined by the calculation and analytical method established by regulatory documents on fire safety.
At the moment, information on the actual fire resistance limits and fire hazard classes of various building structures that have previously passed fire tests is given in the Collections " Technical information(to assist the inspector of the State Fire Service)”, published annually by the Federal State Budgetary Institution “All-Russian Research Institute of Fire Defense” of the Ministry of Emergency Situations of Russia.
Building structures with actual fire hazard classes K1 (low fire hazard), K2 (moderate fire hazard), K3 (fire hazard) can only be used if the required structural fire hazard class of the building is allowed C1, C2, C3, respectively (Table 22 of the Federal Law of July 22 2008 N 123-FZ).
The required degree of fire resistance and the required class of structural fire hazard of buildings are determined in accordance with SP 2.13130.2012 “Fire protection systems. Ensuring the fire resistance of protected objects" (as amended on October 23, 2013) based on certain parameters of the designed building (for example, functional purpose buildings, height of buildings or structures, number of storeys, floor area within the fire compartment, category of the building for explosion and fire hazard, number of seats, etc.).
Further, in accordance with Table N 21 of the Federal Law of July 22, 2008 N 123-FZ, based on the required degree of fire resistance of the building, the minimum required fire resistance limits of building structures are determined.
In accordance with Table N 22 Federal Law N 123-FZ, based on the required class of structural fire hazard, buildings are determined to be minimal required classes fire hazard of building structures.
It is necessary to take into account that fire safety requirements will be met only if the building structure meets both the required fire resistance limit and the required fire hazard class at the same time.
Accordingly, it is initially necessary, based on SP 2.13130.2012, based on certain parameters of the designed building (for example, the functional purpose of the building, the height of buildings or structures, number of storeys, floor area within the fire compartment, number of seats, etc.) to determine the required degree of fire resistance and the required class of structural fire hazard of buildings.
Further, in accordance with Table N 21 of the Federal Law of July 22, 2008 N 123-FZ, based on the required degree of fire resistance of the building, the minimum required fire resistance limits of specific building structures are determined.
In accordance with Table N 22 of Federal Law N 123-FZ, based on the required class of structural fire hazard of a building, the minimum required fire hazard classes of specific building structures are determined.
Further, based on certain minimum required fire hazard classes and minimum required fire resistance limits of specific building structures based on fire test reports or information on actual fire resistance limits and fire hazard classes given in the Collections “Technical Information (to assist the inspector of the State Fire Service)”, select a building structure.
Based on information only about the material from which the building structure is made, it is impossible to determine the actual fire resistance limits and fire hazard classes of building structures.
In accordance with clause 5.4.5 of SP 2.13130.2012, fire resistance limits and fire hazard classes of attic covering structures in buildings of all degrees of fire resistance are not standardized, and roofing, rafters and sheathing, as well as lining of eaves overhangs, may be made from combustible materials, with the exception of specially specified cases.
Gable structures may be designed with non-standardized fire resistance limits, while the gables must have a fire hazard class corresponding to the fire hazard class of the external walls on the outside.
Information about structures related to elements of attic coverings is provided by the design organization in the technical documentation for the building.
In buildings of I-IV degrees of fire resistance with attic coverings, with rafters and (or) sheathing made of combustible materials, the roof should be made of non-combustible materials, and the rafters and sheathing in buildings of I degree of fire resistance should be treated with fire retardant compounds of group I fire retardant effectiveness, in buildings of II-IV degrees of fire resistance with fire retardant compounds not lower than group II of fire retardant efficiency according to GOST 53292*, or perform their structural fire protection that does not contribute to the hidden spread of combustion.
In buildings of classes C0, C1, the structures of cornices, lining of eaves overhangs of attic coverings should be made from materials NG, G1, or these elements should be sheathed with sheet materials of a flammability group of at least G1. For these structures, the use of flammable insulation is not allowed (with the exception of vapor barriers up to 2 mm thick) and they should not contribute to the hidden spread of combustion.
The conditions for the development of fire in buildings and structures are largely determined by the degree of their fire resistance. Fire resistance degree is the ability of a building (structure) as a whole to resist destruction in a fire. Buildings and structures are divided into five degrees according to the degree of fire resistance (I, II, III, IV, V). The degree of fire resistance of a building (structure) depends on the flammability and fire resistance of the main building structures and on the limits of fire spread through these structures.
Based on flammability, building structures are divided into fireproof, non-combustible and combustible. Fireproof are building structures made of fireproof materials. Non-combustible structures are considered to be structures made of materials that do not burn easily or of combustible materials protected from fire and high temperatures by non-combustible materials (for example, a fire door made of wood and covered with sheet asbestos and roofing steel).
The fire resistance of building structures is characterized by their fire resistance limit, which is understood as the time in hours after which 1 of 3 signs occurs during a fire:
1. Structural collapse;
2. Formation of through cracks or holes in the structure. (Combustion products penetrate into adjacent rooms);
3. Warming up the structure to temperatures that cause spontaneous combustion of substances in adjacent rooms (140-220 o).
Fire resistance limits:
Ceramic brick - 5 hours (25 cm-5.5; 38-11 hours)
Silicate brick - ~5 h
Concrete 25 cm thick - 4 hours (the cause of destruction is the presence of up to 8% water);
Wood covered with gypsum 2 cm thick (total 25 cm) 1 hour 15 minutes;
Metal structures - 20 min (1100-1200 o C-metal becomes plastic);
Entrance door, treated with fire retardant - 1 hour.
Porous concrete and hollow bricks have greater fire resistance.
Unprotected metal structures have the lowest fire resistance limit, and reinforced concrete ones have the highest.
According to DBN 1.1.7-2002 “Fire protection. Fire safety of construction projects,” all buildings and structures are divided into eight degrees according to fire resistance (see Table 3).
Table 3
Fire resistance of buildings and structures
| Fire resistance degree | Design characteristics |
| I | Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete using sheet and slab non-combustible materials |
| II | The same. It is allowed to use unprotected steel structures in building coverings |
| III | Buildings with load-bearing and enclosing structures made of natural or artificial stone materials, concrete or reinforced concrete For floors, it is allowed to use wooden structures protected by plaster or low-flammable sheet and slab materials. Requirements regarding fire resistance limits and fire spread limits are not established for coating elements, while elements of attic coverings made of wood can be treated with fire retardant treatment |
| III a | Buildings predominantly with a frame structural design Frame elements - from unprotected steel structures Enclosing structures - from steel profiled sheets or other non-combustible sheet materials with low-combustible insulation |
| III b | The buildings are predominantly one-story with a frame structural design. Frame elements are made of solid or laminated wood, subjected to fire retardant treatment, which provides the necessary limit for the spread of fire. Enclosing structures are made of panels or element-by-element assembly, made using wood or materials based on it. Wood and other combustible materials. enclosing structures must be subjected to fire retardant treatment or protected from the influence of fire and high temperatures in such a way as to ensure the desired limit of fire spread |
| IV | Buildings with load-bearing and enclosing structures made of solid or laminated wood and other combustible and low-combustible materials, protected from the influence of fire and high temperatures by plaster and other sheet and slab materials. Coating elements are not subject to requirements regarding fire resistance limits and flame propagation limits, while attic elements Wood floors can be treated with fire retardant treatment |
| IV a | The buildings are predominantly one-story with a frame structural design. Frame elements are made of unprotected steel structures. Enclosing structures are made of steel profiled sheets or other non-combustible materials with combustible insulation. |
| V | Buildings, the load-bearing and enclosing structures of which are not subject to requirements regarding fire resistance limits and fire spread limits |
Protection of wooden structures from fire:
To protect wooden structures from fire, use:
Impregnation with fire retardants;
Facing;
Plaster.
Fire retardants are chemical substances designed to give wood non-flammable properties (French physicist Gay-Lussac. 1820 Ammonium salts).
Fire retardants - reduce the rate of release of gaseous products, reduce the yield of resin as a result of chemical interaction with cellulose.
For wood impregnation the following is used:
Ammonium phosphate (NH 4) 2 HPO 4
Ammonium sulfate (NH 4) 2 SO4
Borax Na 2 B 4 O 7 * 10H 2 O.
Deep impregnation is carried out in autoclaves at a pressure of 10-15 atm for 2-20 hours.
Soaking is carried out in a fire retardant solution at a temperature of 90 o C for 24 hours.
Impregnation with fire retardants transforms wood into the category of difficult-to-burn materials. Surface treatment prevents wood from burning within a few minutes.
Cladding and plaster - protect wooden structures from fire (slow heating).
Wet plaster - fire protection 15-20 min.