THE SECURITY STAIRS
Emergency stairs or safety stairs are often the only safe way out in the event of fire, or in the event of calamitous events such as earthquakes. In some cases, however, in order to be considered suitable also as “emergency routes”, they must have particular safety features.
Ordinary stairs, in fact, as well as being an indispensable means of communication inside the building, if not compartmentalized, also constitute an element of the building that easily lends itself to a rapid spread of smoke, heat and flames to the upper floors, in quantum, they behave like chimneys in which a “draft” is determined due to the difference in height between the base and the top and this inevitably entails that the staircase is invaded by smoke and quickly not accessible.
Although the Italian legislation does not explicitly speak of fire escape stairs (emergency stairs), with this term in common language we usually refer to three types of stairs, each of which can be used as an escape route in case of need:
1. the external safety stairs;
2. the protected stairs;
3. smoke-proof stairs.
The relative definitions are contained in the Ministerial Decree of 30 November 1983.
The construction of fire escape stairs is mandatory:
- in public buildings or buildings open to the public such as schools, offices, museums, shopping centers and hospitals;
- in hotels and collective accommodation;
- in residential buildings with a fire protection height of at least 12 meters, where it is not possible to approach the fire brigade ladders with at least one window or balcony per floor (e.g. skyscrapers and large multi-storey buildings).
The fire height is the maximum height measured from the lower level of the highest opening of the top floor living space to the level of the lowest external floor: a fire height of 12 meters therefore corresponds to a four-storey building.
The references, by way and exodus stairs, are contained in the Ministerial Decree of 3 August 2015.
In this article we focus on external safety stairs, and in this case those with steel frame and walkways in grated panels.
The safety stairs are stairs that are totally external to the building and must comply with certain characteristics:
1 meter high parapet able to withstand the strong stresses that can derive from a rapid and disordered flow of people;
- Handrail placed retractable protruding no more than 8 cm;
- Ramp width equal to at least 2 modules, or 1.2 meters;
- Rectangular steps with a tread not less than 30 cm and a rise not exceeding 17 cm;
- Straight ramps and with no less than 3 steps and no more than 15;
- Absence of protrusions or recesses for at least 2 meters from the walking surface;
- Landings must have at least the same width as the ramp;
- Trapezoidal steps are allowed, provided that the tread is at least 30 cm measured at 40 cm from the central upright or from the internal parapet;
- The doors leading to the stairs must be equipped with a self-closing device, must open in the direction of the exit, and their opening must not in any way obstruct the flow of people going up or down;
- For buildings with more than two floors above ground, the width of the staircase must be dimensioned by adding the crowds of the two consecutive floors with greater crowding.Below is an example of a fire escape or safety ladder with cage:
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