1、Determination of workersexposure to electromagneticfields and assessment of riskat a broadcast siteBS EN 50496:2008raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsNational forewordThis British Standard is the UK implementation of
2、EN 50496:2008.The UK participation in its preparation was entrusted to Technical CommitteeGEL/106, Human exposure to low frequency and high frequency electromag-netic radiation.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not
3、purport to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2008ISBN 978 0 580 57861 8ICS 17.240BRITISH STANDARDBS EN 50496:2008Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published
4、 under the authority of the StandardsPolicy and Strategy Committee on 31 March 2009 Amendments issued since publicationAmd. No. Date Text affectedEUROPEAN STANDARD EN 50496 NORME EUROPENNE EUROPISCHE NORM November 2008 CENELEC European Committee for Electrotechnical Standardization Comit Europen de
5、Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 50496:2008 E ICS 17.240 English versio
6、n Determination of workers exposure to electromagnetic fields and assessment of risk at a broadcast site Dtermination de lexposition des travailleurs aux champs lectromagntiques et valuation des risques sur un site de radiodiffusion Ermittlung der Exposition von Arbeitnehmern gegenber elektromagneti
7、schen Feldern und Bewertung des Risikos am Standort eines Rundfunksenders This European Standard was approved by CENELEC on 2008-09-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a natio
8、nal standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in
9、 any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Cze
10、ch Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 50496:2008EN 50496:2008 - 2 - Fore
11、word This European Standard was prepared by the Technical Committee CENELEC TC 106X, Electromagnetic fields in the human environment. The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50496 on 2008-09-01. The following dates were fixed: latest date by which the
12、 EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2009-09-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2011-09-01 _ BS EN 50496:2008- 3 - EN 50496:2008 Contents 1 Scope . 4 2 Norma
13、tive references. 4 3 Terms and definitions 5 4 Assessment methods 6 4.1 Worker exposure assessment . 6 4.2 Use of public exposure assessment . 6 4.3 Assessment after technical modification . 7 5 Collection of technical data 7 6 Determination of exposure levels by calculation or measurement 7 6.1 Met
14、hodologies . 7 6.2 Additional considerations 8 6.3 Determination process 10 7 Zoning of exposure work place 11 8 Checking of operating procedures in the different exposure work places12 8.1 Work place access conditions .12 8.2 Signage and delimitation .12 8.3 Specific documentation 13 8.4 Personal p
15、rotective equipment 13 8.5 Safety instructions 13 8.6 Maintenance work 13 8.7 Inspections .14 8.8 Active implantable medical devices .14 9 Information and training 14 9.1 Information for workers 14 9.2 Training of workers 15 10 Assessment report .15 Annex A (normative) Summation formulae .16 Annex B
16、 (informative) Marking .19 Bibliography 20 Figures Figure 1 - Work place assessment process 11 Figure B.1 - Presence of electromagnetic field sources 19 BS EN 50496:2008EN 50496:2008 - 4 - 1 Scope The object of this standard is to provide methods for assessing compliance with the requirements of the
17、 Directive 2004/40/EC 8 at a site operating one or more broadcast transmitters. This standard covers the frequency range up to 40 GHz. NOTE The Council and European Parliament Directive 2004/40/EC will be transposed into national legislation in all the EU member countries. It is recommended that use
18、rs of this standard consult the national legislation related to this transposition in order to identify the national regulations and requirements. These national regulations and requirements may have additional requirements that are not covered by this standard. 2 Normative references The following
19、referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. 1 EN 50413, Basic standard on measurement and calculation proce
20、dures for human exposure to electric, magnetic and electromagnetic fields (0 Hz - 300 GHz) 2 EN 50420, Basic standard for the evaluation of human exposure to electromagnetic fields from a stand alone broadcast transmitter (30 MHz - 40 GHz) 3 EN 50475, Basic standard for the calculation and the measu
21、rement of human exposure to electromagnetic fields from broadcasting service transmitters in the HF bands (3 MHz - 30 MHz) 4 EN 50499, Procedure for the assessment of the exposure of workers to electromagnetic fields 5 EN 62226-2-1, Exposure to electric or magnetic fields in the low and intermediate
22、 frequency range - Methods for calculating the current density and internal electric field induced in the human body - Part 2-1: Exposure to magnetic fields - 2D models (IEC 62226-2-1) 6 IEEE C95.3, Recommended Practice for Measurements and Computations of Radio Frequency Electromagnetic Fields With
23、 Respect to Human Exposure to Such Fields 7 Council Recommendation 1999/519/EC of 12 July 1999 on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz) (Official Journal L 199 of 30 July 1999) 8 Directive 2004/40/EC of the Parliament and of the Council on the m
24、inimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (Electromagnetic fields) Official Journal of 30 April 2004 9 International Commission on Non-Ionizing Radiation Protection, Guidelines for Limiting Exposure to Time-Varying Electric, Mag
25、netic, and Electromagnetic Fields (up to 300 GHz), Health Physics Vol. 74, No 4, pp 494-522, 1998 BS EN 50496:2008- 5 - EN 50496:2008 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 action values the magnitude of directly measurable parameter
26、s, provided in terms of electric field strength (E), magnetic field strength (H), magnetic flux density (B), power density (Seq), limb induced current (IL) and contact current (IC) at which one or more of the specified measures in 8 must be undertaken. Compliance with these values will ensure compli
27、ance with the relevant exposure limit values of 8 3.2 AIMD Active Implantable Medical Device 3.3 antenna device that serves as a transducer between a guided wave (e.g. coaxial cable) and a free space wave, or vice versa 3.4 near-field region region generally in proximity to an antenna or other radia
28、ting structure, in which the electric and magnetic fields do not have a substantially plane-wave character, but vary considerably from point to point. The near-field region is further subdivided into the reactive near-field region, which is closest to the radiating structure and that contains most o
29、r nearly all of the stored energy, and the radiating near-field region where the radiation field predominates over the reactive field, but lacks substantial plane-wave character and is complicated in structure 3.5 broadcasting service radiocommunication service in which the transmissions are intende
30、d for direct reception by the general public. This service may include sound transmissions, television transmissions or other types of transmission e.g. data 3.6 broadcast site site operating one or more broadcast transmitters 3.7 contact current current flowing into the body resulting from contact
31、with a conductive object in an electromagnetic field. This is the localised current flow into the body (usually the hand, for a light brushing contact). Shocks and burns can be the adverse indirect effects. Contact current relates to a short term effect and cannot be time-averaged 3.8 induced curren
32、t current flowing inside a human body resulting directly from an exposure to an electromagnetic field 3.9 employer any natural or legal person who has an employment relationship with the worker and has responsibility for the undertaking and/or establishment (Directive 89/391/EEC) BS EN 50496:2008EN
33、50496:2008 - 6 - 3.10 exposure limit values limits on exposure to electromagnetic fields in 8 which are based directly on established health effects and biological considerations. Compliance with these limits will ensure that workers exposed to electromagnetic fields are protected against all known
34、adverse health effects of electromagnetic fields 3.11 local safety Instruction safety instructions relating to a specific broadcast site and containing the information specified in Clause 8: it must include all the necessary safety-related indications and, if applicable, point out the possible risk
35、of exposure to electromagnetic fields where these are at levels above the worker action values; it could include all the necessary safety-related indications and, if applicable, point out the possible risk of exposure to electromagnetic fields where these are at levels above the limits for the gener
36、al public 3.12 transmitter device to generate the radio frequency broadcast signal which is fed into the antenna system 3.13 worker any person employed by an employer, including trainees and apprentices but excluding domestic servants (Directive 89/391/EEC) 3.14 work place location where workers hav
37、e access as part of their duties; particular place of work within the broadcast site as for example the area near a transmitter with an open enclosure, the area inside a transmitting antenna, on a ladder inside a broadcast mast / tower and platforms under and above the antennas, the area around feed
38、 lines, etc. 4 Assessment methods 4.1 Worker exposure assessment The assessment should be done using the steps outlined below: collection of technical data (Clause 5); determination of exposure levels by calculation or measurement (Clause 6). This includes checking of operating procedures in the dif
39、ferent exposure work places (Clause 8). The results of the assessment process are: zoning of exposure work places (Clause 7); information and training (Clause 9); assessment report (Clause 10). In the case of simultaneous exposure to multiple sources, the combined exposure shall be considered, refer
40、ring to Annex A. 4.2 Use of public exposure assessment If an evaluation has already been undertaken in accordance with the provisions of Council Recommendation 1999/519/EC 7, and the restrictions as specified therein are respected, then the exposure limit values for workers of 8 are also met. BS EN
41、50496:2008- 7 - EN 50496:2008 4.3 Assessment after technical modification After technical modification like maintenance or repair of the installation or the environment, it is necessary to consider repeating or revising the assessment. This is particularly necessary if an additional transmitter or a
42、ntenna is added to a site where there are already one or more transmitters. 5 Collection of technical data Information on the following items may be needed: with regard to the surrounding area - information on the nature of the field from any external sources should be obtained from the operators of
43、 those sources. Examples of useful information are the frequency, the type of service, and whether the transmissions are intermittent. However, it should be noted that much of the detailed information may be commercially sensitive. with regard to the site - the area controlled e.g. information on pr
44、operty, fencing, where the controlled area is bounded, - the site map showing all facilities, e.g. buildings, towers, anchor cables, earth net, - the several areas - where a public assessment has been done in compliance with 7 or national regulation, - where workers have access without specific care
45、, - where workers have only access under specific circumstances. with regard to ELF emissions, the location of all 50 Hz site power supplies or transformers connected to low voltage networks. with regard to the radio-frequency emissions, for each relevant source - the mechanical configuration of the
46、 antennas, geometric dimensions, construction drawings, position in the mast, etc., - radiation pattern, polarisation and gain of antennas, - maximum and nominal power transmitter, - frequency, type of modulation (AM, FM, COFDM, etc.), channel bandwidth, - feeder type and length, attenuation/meter,
47、- additional losses (combiners, patch panels, antenna cables and power dividers). - with regard to scheduling - transmitting time table (especially for short wave), - permitted operating configuration. 6 Determination of exposure levels by calculation or measurement The collection of data permits to
48、 take into account the identification of sources of electromagnetic fields in or around the site during the assessment. However, this standard does not directly address product performance standards, which are intended to limit electromagnetic field (EMF) emissions under specified test conditions. 6
49、.1 Methodologies The work place is often in near field conditions where the situation is rather more complicated than in the far field. This is because the maxima and minima of the E and H fields do not occur together along the direction of propagation as they do in the far field. In the near field, the electromagnetic field structure may be highly inhomogeneous, and there may be substantial variations from the plane-wave impedance of 377 ohms; that is, there may be preponderant E fields
