1、STD-ITU-T RECMN L-21-ENGL 199b 9 4flb257L Ob32972 250 D INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU L.21 (I O96) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Fire detection and alarm systems, detecto
2、r and sounder devices ITU-T Recommendation L.21 (Previously CCITT Recommendation) ITU-T L-SERIES RECOMMENDATIONS CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT For further details, please refer to ITU-T Lisi of Recommendations. STDmITU-T RECMN L-21-ENGL 179b
3、D 48b2571 Ob32774 023 FOREWORD The IT-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (IT). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizin
4、g telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the IR-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Memb
5、ers of the IT-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). IT-T Recommendation L.21 was prepared by IT-T Study Group 6 (1993-1996) and was approved by the WTSC (Geneva, 9-18 October 1996). NOTES 1. telecommunication administration and a recognized op
6、erating agency. 2. follows: In this Recommendation, the expression “Administration” is used for conciseness to indicate both a The status of annexes and appendices attached to the Series L Recommendations should be interpreted as - - an annex to a Recommendation forms an integral part of the Recomme
7、ndation; an appendix to a Recommendation does not form part of the Recommendation and only provides some complementary explanation or information specific to that Recommendation. O ITU 1997 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, el
8、ectronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation L.21 (10/96) 1 1 2 2.1.3 3 STD-ITU-T RECMN L-21-ENGL 177b H 48b257L Ob32775 TbT CONTENTS Introduction Detectors 2.1 Automatic detectors Flame detectors 2.2 Manual detectors . It i
9、s recommended that . 3.1 General 3.2 Circuit design 3.3 Detectors . 3.4 Visual alarms 3.5 Communication with the fire brigade . Appendix I . United Kingdom experience . Appendix II . Japanese experience Appendix III - Argentinian experience . Appendix IV - United States experience . IV.l Building co
10、nstruction IV.2 Fire prevention IV.3 IV.4 Fire system installation and related codes . Telecommunications Equipment Fire Resistance Standards 11 Recommendation L.21 (10/96) Page 1 1 1 2 2 2 2 2 3 4 4 4 5 6 6 6 7 7 7 STD-ITU-T RECMN L-21-ENGL 197b 48b2571 Ob32776 7Tb Recommendation L.21 FIRE DETECTIO
11、N AND ALARM SYSTEMS, DETECTOR AND SOUNDER DEVICES (Geneva, 1996) 1 Introduction In order to protect property and, when applicable, life, protective fire detection and alarm systems can be installed to initiate a number of different activities: - - - emergency evacuation procedures; - summoning of fr
12、e-fighting forces. detection and location of a fire; provision of assistance to contain andor extinguish the fire; It should be noted that a fire detection and alarm system can do nothing to reduce the incidence of fires. It can however reduce the delay between ignition and effective fire-fighting.
13、A satisfactory alarm system for the protection of property will automatically detect the fire at an early stage, raise an effective alarm in time to summon the fire-fighting forces and indicate the location of the fire. An early alarm of fire enhances the safety of personnel by increasing their chan
14、ces of escape. Taking into account the risk of fire and action to reduce the magnitude of danger from fire, quick detection is the first criterion to be considered followed by the activation of extinguishing measures. Detection devices are part of the automatic fire detection and alarm systems. Thes
15、e systems monitor continuously, or at frequent intervals, the physical and/or chemical characteristics of a protected fire area (zone). The function of detectors is to identify fires as soon as possible and, through the control and indicating equipment, to activate alarms and adopt pertinent measure
16、s to extinguish possible fire breakouts, to evacuate personnel and to notify safety and fire-fighting services. These detectors function directly with fire alarm equipment and automatic fire-extinguishing systems, to minimize the damage caused by fire. 2 Detectors 2.1 Automatic detectors In accordan
17、ce with functional characteristics (detection technologies used) and technological characteristics (discrete identification or variable threshold detection), the detectors to be installed are classified as follows. 2.1.1 Heat detectors According to the way in which the sensing is done, they are clas
18、sified as: - Fixed temperature These are designed to operate when they reach a pre-selected threshold temperature. - Rate-ofirise of temperature (differential) These are designed to operate when the environmental temperature rises abnormally quickly. - Combination To respond to boh very slow growing
19、 and rapidly developing fires. 2.1.2 Smoke detectors According to the way in which the sensing is done, they are classified as: - Ionization chamber smoke detectors These rely on the reduction of an electric current flowing between the electrodes in an ionization chamber when smoke particles enter t
20、he chamber. They are particularly sensitive to smoke containing small particles such as are produced in rapidly burning fires. Recommendation L.21 (10/96) 1 - Optical smoke detectors These are designed to operate by detecting the scattering or absorption of light by smoke particles. They are sensiti
21、ve to the larger particles found in optically dense smoke produced by smouldering fires. - Volumetric or beam detectors These work on the principle of optical obscuration and detect the presence of smoke in only a small part of the beam. Some optical beam smoke detectors can also sense thermal turbu
22、lence fiom a fire by detecting the refraction of the beam at turbulent interfaces between hot and cold air. 2.1.3 Flame detectors According to the way in which the sensing is done, they are classified as: - Ultraviolet radiation detectors These use ultraviolet radiation sensitive cells that see the
23、fire directly or through built-in lenses or reflectors. - infrared radiation detectors These use infrared radiation sensitive cells that see the fire directly or through built-in lenses or reflectors. They are designed to respond to the flickering radiation emitted by the diffusion type of flame nor
24、mally found in fires. 2.1.4 Addressable detectors These components of the fire alarm system have a discrete identification that can have its status individually identified or that is used to individually control other functions. 2.1.5 Intelligent detectors These have the capability of modifying auto
25、matically their detection thresholds according to the environmental conditions. 2.2 Manual detectors These manually triggered devices (manual call points) are placed in buildings because they allow an earlier warning to be given than the automatic detection and alam system if personnel are present a
26、t the ignition of a fire. 2.2.1 Manual sounders (audible alarms) Sounders can be used manually to give an alarm of fire. Where there are other parts of the building unlikely to be affected by the fire, the system may be arranged that the sounders are only activated manually only in the zone with the
27、 fire and in adjoining areas for the evacuation of personnel to safe areas. 3 It is recommended that 3.1 General As a fire can start almost anywhere within a building and if undetected grow until extinction becomes difficult or impossible, the highest level of property protection is recommended with
28、 the detection and alarm system installed throughout the building. 3.2 Circuit design The design of a fire detection and alarm system should provide reliable facilities for transmission of signals to the control and indicating equipment from manual call points (manual detectors) or automatic detecto
29、rs and for the transmission of any resultant fire signal to both sounders and ancillary equipment which is operated by the fire detection and alarm system. An indication should be given of any fault in the wiring circuits or power supply without giving a false fire alarm. 2 Recommendation L.21 (10/9
30、6) STD-ITU-T RECMN L-21-ENGL 299b 48b257L Ob32978 779 A fault in one zone should not affect the operation of the fire detection and alarm system in other zones of the building. Disruption during maintenance and testing should be minimized. Where sounders use the same wiring as detectors, no alarm so
31、under should be affected by the removal of a detector for maintenance. Where a sounder is removed for maintenance, a fault warning should appear at the control and indicating equipment. Where microprocessors are used in fire detection and alarm systems, their memories should be protected against una
32、uthorised interference. Also, their operation should be continuously monitored for accidental corruption, for example by transient interference. 3.3 Detectors Suitable detectors should be placed in all zones (fire areas) which are to be fire protected and should convey an alarm to the control and in
33、dicating equipment either by hard wiring or by wireless. The combustion characteristics of all materials present in a fire area (zone) should be analysed to ascertain the type or types of detector to be installed. In accordance with functional characteristics (detection technologies used) and techno
34、logical characteristics (discrete identification or variable threshold detection) the detectors to be installed are classified as follows. 3.3.1 Heat detectors These devices should be placed in fire areas (zones) with defined temperature thresholds and where smoke may normally be present, that is in
35、 kitchens and diesel engine rooms. 3.3.2 Smoke detectors These devices should be placed in fire areas (zones) where ignited elements generate smoke before breaking out into flames. 3.3.3 Flame detectors These devices should be placed in fire areas (zones) to detect flames from ignited elements. 3.3.
36、4 Intelligent detectors These devices should be placed in fire areas (zones) in buildings of high complexity and with a diversity of combustible elements, equipment and personnel. They may be either smoke or heat detectors. 3.3.5 Manual detectors (manual call points) These devices should be placed i
37、n fire area (zones) fiequented by personnel. They should be located on exit routes and floor landings of stairways, located within a specified distance (for example, 30 m) of personnel work places and be easily identifiable against a contrasting background. 3.3.6 Manual sounders (audible alarms) The
38、 acoustic signalling devices of the fire alarm system should be distributed throughout the building so that its signal emitted either automatically or manually would be audible in any place. In rooms containing customers and service personnel, the acoustic signal should be of lower power, though per
39、fectly audible, because the permanent presence of personnel ensures detection of the alarm at lower power levels. If the loudness level is very high it could induce panic, nervous excitement and confusion in the customers. The sounder frequencies should preferably be in the range of 500 Hz to 1 O00
40、Hz. Buildings of several floors should have at least one audible alarm per floor. The wiring of sounder circuits should be arranged so that in the event of a short circuit developing in any part of the circuits due to the fire, at least one sounder will continue to operate. This minimum provision sh
41、ould ensure that a general alarm can be given at the start of a fire and for a significant period thereafter. Where the single sounder is not audible throughout the building, sounder cables likely to resist fire for a sufficient period should be used. Recommendation L.21 (10/96) 3 STD.ITU-T RECMN L.
42、21-ENGL 1b 48b259L Ob32979 b05 m Where the fire detection and alarm system extends to other parts of the building unlikely to be affected by the fire, the system may be arranged such that the alarms sound in the area (zone) with the fire and in adjoining areas, for the evacuation of personnel to saf
43、e areas. Or the system may be arranged such that the alarms only sound in the zone with the fire. It should not be possible to prevent the transmission of the alarm by the act of silencing the alarm sounders nor should it depend on the state of any silencing switch. 3.4 Visual alarms In areas where
44、high sound levels may persist for more than 30 s, (for example, in diesel rooms with an engine running) visual alarms (for example, in the form of a flashing light) should be used. The wiring of the circuit should be arranged with the same precautions as those described above for sounders (audio ala
45、rms). 3.5 Communication with the fire brigade The responsibility of calling the fire brigade should be both clearly specified and understood. A special telephone line should be routed through the building to avoid areas where fire is likely to start or spread rapidly. The line should be barred from
46、receiving incoming calls and it should only be used for emergency outgoing calls. Appendix I United Kingdom experience Within the United Kingdom, British Standard BS 5839 takes into account the work of ISOTC 21/SC 3 - Fire detection and alarm systems. The various parts of the British Standards speci
47、fication are: - BS 5839: Part 1 - Fire detection and alarm systems for buildings. Part 1 - Code of practice for system design, installation and servicing. - BS 5839: Part 2 - Fire detection and alarm systems for buildings. Part 2 - Specification for manual call points. - BS 5839: Part 3 - Fire detec
48、tion and alarm systems for buildings Part 3 - Specification for automatic release mechanisms for certain fire protection equipment. - BS 5839: Part 4 - Fire detection and alarm systems for buildings. Part 4 - Specification for control and indicating equipment. - BS 5839: Part 5 - Fire detection and
49、alarm systems for buildings. Part 5 - Specification for optical beam smoke detectors. British Standard BS 5445 covers parts of EN 54 components of automatic fire detection systems produced by Technical Committee CENTC 74. These are: - BS 5445: Part 5 - Components of automatic fire detection systems. Part 5 - Heat sensitive detectors - Point detectors containing a static element. 4 Recommendation L.21 (10196) STD*ITU-T RECMN LeZL-ENGL 199b 48b257L Ob32980 327 - BS 5445: Part 7 -Components of automatic fire detection systems. Part 7 - Specification for point type smoke detectors u
