The most terrible element at all times was considered fire. Much water has flowed since then, as Prometheus taught people to enjoy its benefits. The acute issue of fire safety. Especially dangerous fire in high-rise buildings, at the same time accommodating a large number of people.
The types of smoke-free stairwells
Most people, who are victims of fire, die from smoke inhalation and carbon monoxide, so it is important to provide smoke-free escape routes in the event of suspicion of a possible fire. The main means of evacuation from high-rise buildings have been and still remain a flight of stairs. Construction norms and rules (SNiP) provide three types of smoke-free stairwells: H1, H2 and H3.
According to the construction norms and rules there are three types of the smoke-free stairs divided:
- H1 – the stairs, the entrance to which is via the open space outside the building;
- H2 – staircases with additional air pressurization;
- H3 — the staircase, the entrance to which is through specially created zone with overpressure air.
General requirements for smoke-free stairs
According to the rules of fire safety smoke-free all staircases must be fitted with emergency lighting. The width of a doorway must be not less than 1.2 meters, and its height shouldn’t exceed 1.9 meters. The exit stairways should not be held already by the width of the span. If smoke-free cage is arranged through a wall with the elevator shaft, the wall air vent is arranged at the upper floor for free access of air.
Personal things shouldn’t be placed in the passages to smoke-free stairs and landings. It is forbidden to mount partitions that are not noted in the project. It is also impossible to cut openings in existing fire protection bulkheads.
Smoke-free stairways must be equipped with handrails and non-flammable little heating materials.
Smoke-free stairs of the first type (H1)
In accordance with “Construction norms and rules” the buildings above thirty feet must be designed with staircases of the H1 class. This type of device requires stairs, which can be reached from the landing floor through space with the open air. Design feature of such structures is that they are not directly connected with the floors of the building.
Usually H1 stairwells are located in the corners of the buildings and structures on the windward side and have the transitions of balcony, shielded screens.
The transition can be performed in the form of loggias or open galleries, the width of the aisle shall be not less than 1.2 meters. The width of the wall between the passages, as well as the span nearest the window may not be less than two meters.
Aisle width must provide the transportation of fire-affected people on stretchers!
Device of the smoke-free stairs of the second type (H2)
Stairs, arranged by H2 type, as recommended in the top floor buildings, have height from twenty-eight to fifty meters. Air overpressure in the stairwells of H2 type is arranged on the principle of thrust of the kiln and may be permanent or operable in time of fire alarm. There can be also the device of self-pressurization of the air pumps.
Electric pumps, providing air pressure should be equipped with an uninterruptible power supply.
The thrust (or pressurization) should be carefully designed when designing ventilation. The pressure should be such that fire doors to the stairs should be opened by any man. The lower level pressure on the door should not be less than twenty Pascals, on the top – not more than one hundred and fifty Pascals.
The entrance to stair flights of H2 type is arranged across entryways or gateways, equipped with fire doors of the appropriate category.
It is advisable to provide smoke-free stairwells of the second type with vertical partitions every seven or eight floors. Air backup is mounted in the upper zone of the resulting compartments.
Smoke-free stairs of the third type (H3)
The third type smoke-free stairwells also uses air backup. Unlike stairwells, arranged according to the H2 type, the device has special facilities with self-closing door closers for the passage of people. The size of the premises shouldn’t be less than four square meters. Air backup in the stairwells of this class is occupied by both the staircase space and arranged gateways. Thrust air can be carried out on a continuous basis or activated automatically during a fire or smoke.
The main material used in the construction of evacuation smoke-free passages, is concrete. Concrete safe in the fire relation is durable and easy to operate. The use of steel structures, such as fences or doors, is a supplement to the concrete base. Also the use of metal spans can be justified in light building constructions.
The use of wooden elements is possible in a small volume, such as wooden door handles or handrails after processing with fire-fighting means.
Other types of construction materials are not used in the composition of smoke-free ladders.
Other types of emergency structures
Other structures can be used alternatively to smoke-free ladders. For example, stairwells of L1 and L2 types with natural light through the window openings.
Also there are various fire escapes outside of residential and public buildings according to All Union State Standard. In the event of a fire, the evacuation is carried out and the fire-fighting equipment is delivered using these stairs.
This article describes in detail the smoke-free stairwells. Why do we need them and what are their kinds? In addition, there are the general principles of fire safety in relation to the landings. Our website is devoted to the stairs, and all that is connected with them, so you should ask questions, offer interesting topics for articles – our writers will fulfill any wishes of site visitors.