The current level of development of scientific and technological progress does not affect the existence of the fact that the fire for millennia has been and remains one of the most dangerous enemies of the human home.
Despite the widespread introduction of rules prescribing the use of exclusively non-combustible materials for interior decoration, statistics remain implacable: people’s housing is by no means invulnerable today.
Often the only thing that remains in the event of a fire to residents is to flee, that is, to evacuate. The safest escape route from multi-storey buildings is fire escape stairs.
The danger to people in case of fire is not only fire. Smoke is also dangerous. But the most terrible invisible enemy is carbon monoxide. A person may not notice its effects (unlike ordinary burning, carbon monoxide does not have a smell or color). Carbon monoxide poisoning is characterized by rapid development. After a few minutes, the victim may lose consciousness, after which he practically has no chance of salvation.
Therefore, in every house, as a most important condition for rescuing residents during a fire, non-smoke stairwells are equipped. What are the types of smoke-free staircases and stairwells?
Stairs - an integral element of buildings
The staircase is an integral element of high-rise buildings. Distinguish between conventional structures that serve to communicate floors, as well as emergency stairs, i.e., smoke-free.
The presence of the latter is the most important condition under which evacuation in case of fire is provided. For a number of buildings, it is dictated by the SNIP, therefore, they are necessarily provided by architects when creating the design of structures.
Evacuation stairs: appointment
Evacuation stairs must certainly be present in high-rise buildings. Such designs ensure the safety of residents during a fire or in case of other emergency situations. The arrangement of evacuation stairs in various types of buildings is subject to certain standards regarding their size, configuration and placement. Regardless of the type of model, the general purpose of these structures is to ensure the safe exit of people from the building if necessary.
Residents of the house, employees and visitors to the institution, using the escape stairs, can leave the room without danger to life and health. An emergency exit is designed to protect them from fire and smoke. It is very important to ensure free access to it for everyone in the building.
Evacuation stairs can be used as an alternative exit from the premises. This is true for structures not equipped with a separate back door. Fire safety rules prohibit the operation of buildings above three floors that are not equipped with an emergency staircase.
Location
Separate requirements are presented to the location of the emergency stairs. Typically, their placement is designed at the rear of public buildings or from the end if an open exit is planned.
With the proposed arrangement of the evacuation exit inside the building, a separate room or corridor is allocated for such a staircase. This is necessary in order to ensure the safety of people descending in the event of a fire and prevent the blocking of the often the only possible way out of the house.
Such a room should be equipped with a fireproof door, which is capable of containing flame for at least 1 hour. At the same time, it is important to ensure the sealing of joints and rapid smoke removal.
Each floor should be equipped with access to the stairwell. Its width depends on the size of the passage and steps. Semi-closed models provide for the location within the premises of the site, the door from which leads to an external staircase. This is an excellent option for cases where it is impossible to completely isolate the passage from the smoke.
For outdoor outdoor types, a special rule applies: the distance from the edge of the stairs to the wall should be from 100 cm. This reduces the risk of fire entering the emergency exit and prevents the structure and protective handrails from heating up.
Materials
Since this design is intended for use in extreme situations, including during fires, certain requirements determine the choice of materials used for its construction. The main condition is to ensure the strength and fire resistance of the stairs. Therefore, the most popular are materials such as concrete and metal.
The use of materials that are flammable, crumble, or release toxic substances when heated is strictly prohibited.
SNIP and GOST requirements
GOST and SNiP standards govern the standards by which all types of stairs are installed. They relate to evacuation models.
- The standard slope of the evacuation ladder is one in which the ratio of the length and height of the span is 2: 1.
- For March 1, the presence of 3-18 steps is permissible. For 2-marching, their number should not exceed 16 pieces.
- The width of the tread should serve to ensure comfort of movement, the optimal size is 24-29 cm.
- The height of the step is usually 20-22 cm.
- The width of the stairs is provided for by requirements such that 2 people can walk along it at the same time. The smallest permissible value is - 1 m. It is allowed to reduce the dimensions for external structures to 70 cm.
- The area between the marches in size should correspond to the width of the stairs and the exit to it.
- To ensure the safety of evacuation from the building in case of fire, it is necessary to provide access to a staircase that leads to an open space or to a separate room, protected from fire and smoke.
Classification
Evacuation ladders are classified by type of material, location, as well as design features. There are three main types of modern evacuation ladders, which differ in such characteristics as purpose, width and configuration:
- placed on special smoke-free stairwells inside the building;
- located inside the building, and is not fenced by walls;
- located outside and is an emergency exit design.
The latter is used exclusively for evacuation, while the first two types of stairs sometimes replace the main entrance.
About permissible types of structures
For evacuation, direct marches equipped with intermediate sites are also used. In some cases, when there is not enough space for their location, in parallel or with a slight inclination to the wall, vertical structures like firefighters are installed.
Categorically prohibited
The rules of fire safety forbidden to erect stairs:
- with running steps;
- with curved and irregular spans;
- screw;
- with steps of different sizes.
What are smokeless stairwells?
The presence of such structures in the house is designed to ensure maximum safety of life and health of people in case of fire. They represent marches of certain sizes, which should be located in suitable areas of the building.
One of the main requirements for an emergency exit is its isolation from smoke. Smoke-free stairwells are distinguished by the fact that during a fire RPPs (fire, smoke, etc.) do not get into them.
The presence of these structures ensures successful evacuation in case of fire in multi-storey buildings. Different requirements are presented to them depending on the specific type.
Types
Smooth stairwells are divided into several types, which can be classified by specific structural features that distinguish them, location, access to them and principles of operation. Types of stairwells:
- H1 is considered the base model. Characteristic features of the design is the availability of access through an open area. It is necessary to have a smoke-free approach to the emergency exit.
- H2 provides for air pressure in the event of fire.
- H3 is an analogue of H2, but provides for access to the march through the vestibule-gateway. An additional air supply is also provided, which is supplied both during ignition and on an ongoing basis.
Requirements
Fire safety on stairwells is ensured by rules that provide for the preservation of human life:
- All smokeless staircases are equipped with emergency lighting.
- The width of the doorway should be from 1.2 m, and the height - from 1.9 m.
- The width of the exits from the flights of stairs should not be narrower than the span.
- When installing a smoke-free cage adjacent to the elevator shaft, a ventilation hole (at the level of the upper floor) is arranged in the wall to ensure free air access.
- No personal items are allowed in the walkways to the non-smoke stairwells. The staircase should be uncluttered, as trash can interfere with the evacuation of people and the work of firefighters.
- It is forbidden to independently install partitions not provided for by the construction project, as well as cutting openings in existing fire-prevention bulkheads.
- Necessarily equipping non- smoke stair flights with handrails made of non-combustible materials and slightly heating.
Smokeless stairs H1
“Building norms and rules” say: in buildings with a height of more than 30 m, smoke-free staircases of the H1 type must be arranged.
This view requires the installation of stairs that can be accessed from the floor area, using open air space for promotion. The location of H1 may be a veranda, a balcony or a fenced entryway, taken out of the premises. This is due to the need to ensure natural isolation from the smoky part of the evacuation exit building. The best option for placing this type of staircase is the corner of the building. The most advantageous position is the inner corner, equipped with additional piers. Their design feature is the lack of direct connection with the floors of the building.
The usual placement of H1 cells is in the corners of buildings on the windward side. They are characterized by the presence of transitions of a balcony type, as well as fences with the help of protective screens. The transition is carried out in the form of an open gallery or loggia, a passage width of 1.2 m must be provided. The width between the aisles, as well as the gap from the wall to the window, must be at least 2 m.
Smooth stairs H2
An H2 staircase is located in a building, the upper floor of which is located at an altitude of 28-50 m. Air cells are created in the H2 cells (the principle of stove draft). It can be permanent or opens in case of fire alarm. It is also possible to install an autonomous back-up using air electric pumps that provide air pressure, which must be equipped with uninterruptible power supplies.
When designing ventilation, you must correctly calculate the traction force (or back pressure). Pressure should provide the possibility of free opening of fire doors to the stairs. The pressure on the lower floor should be at least 20 pascals, on the upper - no more than 150 pascals.
Tambours or locks through which entrance to the stairwells of H2 is provided are equipped with fire doors. In non-smoky cells of this category, it is advisable to arrange vertical partitions with an interval of 7-8 floors.
Smokeless stairs H3
The non-smokable stairwell H3 is also constructed using air pressure. Their difference lies in the arrangement of special passage rooms with self-closing doors. Their sizes should be at least 4 square meters. m. In cells of this type, air is kept in the space occupied by the stairs and into special locks. Air draft is carried out on an ongoing basis or is automatically activated in case of fire or smoke.
Main materials
When creating evacuation smoke-free passageways, concrete is most often used. It is fireproof, durable and easy to use material. As a complement to the concrete base, steel structures are used, for example, in the manufacture of fencing or doors. Metal spans are also justified in lightweight structures.
Wooden elements are used in small volumes: wooden handrails or door handles, which must necessarily be treated with fire fighting compounds.