Role of elevators in fire safety of high-rise buildings

A little history

Passenger elevators in their modern form are a consequence of the emergence of high-rise buildings, which in turn is caused by the desire to maximize the use of the space allocated to the building.

The first building to have a passenger elevator was the five-story, 24-foot EV Haughwout New York City, at the corner of Broome Street and Broadway, built in 1857, designed by John P. Gaynor, The elevator was intended for wealthy visitors to the fashionable store housed in the building. The elevator was powered by a steam engine installed in the basement and served an advertising purpose. The speed of movement was 0.2 meters per second.

The first high-rise building, 10 floors, 42m - HomeInsuranceBuilding, "skyscraper", as it was then called, was built in Chicago in 1885. In this project, architect William Le Baron Jenny first realized the idea of load-bearing frame, the main method of skyscraper construction used to this day.

For example, the "symbol of America" in New York - Empire State Building, 102 floors, height of 381 m to the roof and 443.2 m to the top, completed on May 1, 1931, was built using this technology,

and the tallest building Burj Khalifa - 163 floors (plus an additional 46 in the spire and 2 in the foundation), 828 m, completed on January 4, 2010.

A high-rise building without elevators does not have the required functionality. The elevator is an integral part of the building.

There are 73 elevators in EmpireStateBuilding. In the Burj Khalifa building there are 57 elevators with a speed of 10 meters per second.

Fire is a major hazard for high-rise buildings

A high-rise building is exposed to many dangers, but the main one is the danger of fire. The existing statistics of emergency accidents in high-rise buildings fully confirms this.

Starting from heights of 80 m, evacuation of people and fire extinguishing using elevators mounted on special vehicles is extremely difficult.

Therefore, an elevator is almost the only way for firefighters and rescuers to get to the heart of the fire quickly. To do this, the elevator must remain operational for a given time after the fire has started. Such an elevator is called an elevator for transporting firefighting units.

In order to better understand elevator solutions for firefighters, let's first briefly review general approaches to fire safety in high-rise buildings and then, in this context, the requirements for elevators to transport firefighting units.

Approaches to ensuring fire safety of high-rise buildings

The main approaches to fire safety of high-rise buildings are:

Lack of "single points of failure" in power supply systems, operational communication within the building, fire detection, fire extinguishing, smoke removal.
Availability of redundant power inputs from independent substations.
Utilizing cables and busbars of specified fire resistance to power critical safety and firefighting systems.
Use only cables that do not support combustion and do not emit toxic gases.
Availability of an autonomous diesel generator for the most critical, in terms of fire safety, systems.
The availability of elevators that remain operational long enough to transport firefighting crews to the burn area. Such elevators are referred to as "fire department transport" elevators.
A battery in the elevator drive system to allow the elevator to descend to the nearest stairwell in case of external power failure.
Zoning of the entire building into fire compartments. The fire compartment must start from its technical floor. All fire compartment enclosures must have a guaranteed, predetermined fire resistance. The laying of communications (cables, busbars, pipelines, air ducts) between compartments must be carried out through fire-resistant passageways with a fire resistance limit not lower than the fire resistance limit of these enclosures.
The area of the fire compartment and its height shall not exceed the standard.
The fire compartment shall contain rooms of the same functional fire hazard class.
Availability of special "rescue" rooms equipped with clean air pressurization systems where occupants and staff could wait for rescuers.
Rescue and other rooms should be stocked with personal protective equipment.
Availability of reserve water tanks installed on technical floors to ensure autonomous operation of drip fire extinguishing systems.
The elevator shaft for one or more elevators must be designed as a fire compartment from the point of view of building structures. Only fire-resistant elevator doors shall be used.
A group of stairwells connected by flights of stairs shall be executed as one or more fire compartments.
Passages between fire compartments must be made only through airlocks and vestibules with doors of standardized fire resistance that do not allow the passage of gases and smoke. The doors must be equipped with door closers.
The width of doors, stairwells, the size of airlocks and vestibules shall be selected so that wheelchairs and rescue stretchers can pass through.
There shall be at least two elevator shafts running through each floor, spaced as far apart as possible from the floor dimensions.
There shall be at least two stairwells on each floor, spaced as far apart as possible (if other requirements are met).
An air supply system shall be provided for the elevator shaft to prevent the products of combustion from entering the shaft.
Air supply and smoke extraction systems shall be provided for stairways.
Public premises located at a height of more than 50 m shall not have a capacity of more than 100 persons.
If restaurants, cinemas, fitness centers and other social and cultural facilities with a capacity of more than 50 people are located in buildings at a height of more than 50 m, the distance from the doors of these facilities to the smoke-free stairwell should not exceed 20 m.
Premises with a design capacity of more than 500 people should be designed as a fire compartment, i.e. have fire-resistant walls and ceilings, the distance from these rooms to smoke-free stairwells should not exceed 20 m.
The number of elevator shafts crossing all fire compartments, as well as any one group of consecutive compartments, shall be the minimum necessary.
Only fully insulated fire-resistant elevator shafts may be used. The use of mesh and other "open" elevator shafts is not permitted.
A minimum of one elevator capable of operating in a fire department transport mode shall be provided at each floor stop.
The use of air supply systems in elevator shafts is mandatory.
Elevator doors (except for doors leading to the first floor lobby) should lead only to a vestibule or airlock, separated from other rooms of the fire compartment by a vestibule with doors of a given fire resistance.
Exit from the fire compartment to the stairwell (to the stairwells) is carried out only through a vestibule or airlock with doors of the specified fire resistance.
If the building has different functional areas, e.g. residential and business, they should belong to different fire compartments and (if possible) have their own entrance.
Vestibules or airlocks shall be provided for access to the flat roof.
The flat roof shall be provided with an area for safe landing of the helicopter. As a last resort, a platform shall be provided on which the helicopter could lower a rescue container
Install emergency elevators - elevators ("lifeboats") in different parts of the building, especially on roofs, for quick evacuation of people in case of fire.
For the distribution of electrical power to the building's rooms, busbars in steel protective boxes with a specified fire resistance limit should be preferred.

As follows from the above, ensuring fire safety is a complex systemic task, when solving which designers should take into account many factors, ranging from the functional purpose of the designed building, climatic and other natural conditions and ending with the choice of construction and structural materials, engineering solutions and specific types of systems and devices.

GOST R 52382-2005. Elevators for firefighters

Since our task is to determine the role of elevators in ensuring fire safety, let us first of all refer to GOST R 52382-2005, "Elevators for firefighters". We also recommend to familiarize ourselves with the document "Rules of device and safe operation of elevators, PB 10-558-03".

This GOST not only establishes rules for zoning of premises inside a high-rise building, fire resistance limits, but also conceptually describes approaches to the use of elevators for firefighters in firefighting.

At the same time, realizing the complexity of fire safety in high-rise buildings, the standard contains a restrictive note:

"Fire resistance limits for the enclosing structures of shafts, machine rooms and elevator halls of elevators for firefighters, as well as the fire resistance limits of shaft doors, doors of machine rooms and elevator halls, are valid for residential buildings up to 75 m high, buildings of other classes of functional fire hazard with a height of not more than 50 m and buildings with no more than one underground garage.

For buildings of greater height, as well as for particularly complex and unique buildings, technical specifications reflecting the specifics of their fire protection shall be developed, including a set of additional engineering, technical and organizational measures.".

Considering that residential assignments higher than 75 m are still exotic, the standard covers the practical needs of a wide range of specialists and provides basic knowledge to start designing higher structures.

Passenger elevators and elevators for firefighters

Independent use of elevators by occupants (staff) in case of fire is prohibited.

According to current regulations, after the "Fire Alarm" signal, the elevator must ignore any newly received calls and orders. If the car is moving upwards, its direction of travel is reversed. The elevator moves to the exit floor for evacuees, where the doors automatically open. Further movement of the elevator is possible only if it is an "elevator for transporting firefighters" and only in the "fire hazard" mode.

Elevator for transportation of fire units (Elevator TPP) is an elevator equipped with control, protection and communication systems, providing the movement of fire units to the floors of buildings (structures) in case of fire.

Under normal operating conditions, the CCI elevator operates in the same way as other elevators in the building - in individual or group mode.

The firefighter operates the elevator only from the cab and only the firefighter has the authority to make the decision to use the fire department elevator to evacuate injured or endangered persons using the fire department elevator.

Conceptually, GOST R 52382-2005 considers the building as follows (Figure 1).

Figure 1. Fireproof rooms in the building.

1 - elevator shaft, forming a separate fireproof room and passing through all floors of the building; 2 - staircase (escape route), forming a separate fireproof room and passing through all floors of the building; 3 - fireproof elevator halls, each of which forms a separate fireproof room on each floor; 4 - useful areas of the building, which on each floor may have one or more fireproof rooms

Fire-resistant building structures limit the volumes of the elevator shaft, staircase, elevator halls (these are separate fireproof rooms), useful areas of the building. Passages between them are realized through fireproof doors.

Usually the elevator drive is located in a protected elevator shaft, if it is located in the adjacent room, the fire resistance of the partition (floor) separating the machine room from the shaft is not standardized. The elevator shaft and machine room is equipped with a ventilation system and the creation of excess air pressure. All passages through the elevator shaft are equipped with fireproof barriers with the required fire resistance limit.

The standard states that the following measures shall be taken to ensure the operability of the CCI elevator and to ensure the safety of firefighters:

Fire resistance of doors of shafts, elevators, vestibules, airlocks is not less than EI 60. This means that the door will not lose its integrity and heat-insulating capacity within 60 minutes after the start of a fire.
Due to overpressure in the shaft it is assumed that microcircuits and other elevator control and signaling elements will not heat up to more than 65^○ C by the time firefighters arrive at the fire area.
Elevator car and drive electrical devices are protected against flooding with water used for fire extinguishing.
The elevator cabin is equipped with hands-free communication with the control center (without using a handset).
The elevator cabin is made of non-combustible materials and materials of permissible fire resistance classes.
There is a hatch in the roof of the elevator car that allows the firefighter to access the roof. A ladder is attached inside or on the outside of the car, which allows the firefighter to reach the elevator door locking mechanism of the nearest upper floor.
The locking mechanism of elevator doors is designed so that a firefighter can open it from the inside without excessive force.
All electrical wiring and flexible loop of the cabin are made by cables of specified fire resistance in accordance with Chapter 5.5 "Electrical Equipment of Elevators" Section 5 of the PUE, 7th edition.
Power supply of elevators for firefighters is performed as for a special group of electrical receivers of the I category.
The power supply to all elevator systems is reserved (Figure 2.).

Figure 2. Electricity supply scheme of CCI elevators.

1 - main power supply source; 2 - backup power supply source; 3 - power supply distribution; 4 - automatic switching from main to backup; 5 - ordinary elevators; 6 - elevators for firefighters; 7 - other important building equipment; 8 - other ordinary elevators included in a group installation with an elevator for firefighters.

Variants of firemen elevator placement in elevator shafts according to GOST R 53296-2009

GOST R 53296-2009 "Installation of elevators for firefighters in buildings and structures. Fire safety requirements" is the second, very important standard of direct action. In many respects its requirements coincide with the requirements of GOST R 52382-2005, "Elevators for firefighters".

This standard addresses 4 options for the placement of a CCI elevator in a shaft and the fire resistance requirements associated with each type of placement for the structures used.