Description and Applications
The smoke and heat evacuation systems (EFC), are made up of natural or mechanical ventilation of rooms with manual or automatic operation, sometimes coupled with smoke curtains are covered in Directive 89/106/EEC, adopted in Italy by DPR n. 246 dd. 31.04.1993. This standard is harmonized as a technical specification adopted by CEN (Comite Europeen de Normalisation), in particular, that is in compliance with Technical Committee CEN / TC 191 named “Fixed to fight the fire “. AI operates inside a working group that is developing the Community rules on EFC systems and technical specifications of all its components.
The contents of the UNI 9494 are in perfect harmony with the provisions of the projects of the CEN / TC 191. The EFC are usually constructed according to the latest European technical standard UNI EN 12101 transposed into Italian and published as UNI EN 12101-2-2004.
These systems are used to extract the fumes from the airlines concerned and the heat generated by a fire, helping to contain the lateral propagation and to create under the state of fumes in the suspension area free from fumes themselves, thus guaranteeing to maintain mackerel from combustion products evacuation and escape routes and access for fire-fighting operations.
It also helps to delay or prevent flash over (generalized fire) and to reduce the risk of collapse of the structural elements of the area due to the increase of temperature.
Obviously their limit lies in limiting the use that is reserved for single-storey buildings and / or the top floor of multi-storey buildings, it is not possible their use in intermediate floors.
The purpose of the system is EFC may therefore summarize thus:
- facilitate the evacuation of the present and the work of the emergency services;
- protect structures and goods by the action of smoke and hot gases and reduce the risk of collapse of supporting structures;
- delay or avoid full fire
- reduce damage by the combustion gases and from any toxic and corrosive substances generated by the fire.
The effective action of the system of smoke and heat evacuation occurs in the first stage of the fire, with temperatures up to 300 ° C. It therefore emphasizes that the EFC systems, like all other fire protection systems, shall come into operation in the first minutes after the outbreak of the fire. The UNI 9494, already in the definitions and terms, introduces the compartment (A), sector limited by building walls and ceilings resistant to fire and the compartment ceiling (As), area between two walls or between smoke-tight two structural elements similar (for example beams).
Paragraph 5 of the UNI 9494 defines how the system should be designed.
The EFC must meet a number of features that the manufacturer must satisfy. Every single EFC has its own opening command with an independent source of energy and thermal release at 68, 93 or 141 ° C. The autonomous source of energy is a cartridge containing 30 g of CO2. Each group of EFC, group that covers a compartment or a part of a compartment (generally areas from approximately 1600 m2), has its own command to open fire. This remote control is the most important because it provides ventilation fire, evacuation of smoke and hot gases from the area under fire.
In paragraph 6 of the UNI 9494 parameters that are taken into consideration are the speed of propagation of the fire, the expected duration of the fire itself, the geometry, ie the compartment.
With the first parameter you want to consider the amount of smoke and hot gases produced. Do not require the fire load, but the speed with which the brazier widens. And you give three hypotheses:
It is not easy to use the low speed, because they are just a few plastic packaging to bring the case to the average speed. The speed is high in products and substances with rapid combustion, almost all players. The second parameter, the development time of the fire, is given by the sum of the alarm time (O min. With automatic smoke detection, 5 min. In the presence of men) and the time for action by the fire brigade, 5 min. for internal team, 20 min. for external team. It keeps tripping time lowest, 5 min., If any automatic shutdown as the sprinkler.
The trip time is given by the external team of firefighters. In general, it is estimated 1km = 1 min., In areas with difficult traffic, it is advisable to confirm the time from the provincial command.