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Jun 03, 2018



Bradley Hahn
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    Radio Frequency Hazards To JSP 482 Edition 4

    Electro-Explosive Devices

    CHAPTER 24





    1.1 Introduction1.2 Statutory Requirements


    2.1 Factors Affecting Susceptibility2.2 EED Testing for Susceptibility to EM Radiation2.3 Minimum Separation Distances from Radio Frequency Sources for Explosives Containing

    EED2.4 Storage and Transport2.5 Storage and Processing Considerations


    3.1 Introduction3.2 Inside Explosive Licensed Buildings

    3.3 Mobile Phones and Pagers


    4.1 Introduction4.2 Anti-Theft Tracking Devices4.3 Emergency Transportation Procedures

    PageReferences 9


    1 Reference Level for Occupational Exposure 22 Reference Level for General Public Exposure 33 EED RADHAZ Categories 4

    AnnexA Sensitivity of EED and their Firing CircuitsB Safe Distance Calculations for use of Radio Transmitting Devices Inside an Explosive

    Licensed BuildingC Electromagnetic Radiation Hazards in Operational Bases

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    1.1 Introduction

    1.1.1 Over recent years there has been a significant increase in the use of electroniccommunication/detection devices throughout all sections of the community. Types of appliances

    now in common use range from management/control aids, telemetry, mobile telephones andwireless communication links (Wi-Fi, LANs) to a growing variety of high-powered transmitterscovering voice communication, electronic data transmission and radar.

    1.1.2 These equipments produce radio frequency (RF) fields of varying intensity according totheir output power and antenna gain and are potentially hazardous when used in close proximity toexplosives that have an installed electrical means of initiation. This initiation, generally by anelectro-explosive device (EED), occurs since most EED function as a direct result of heating theinitiating material by an input of electrical energy which can be derived from an external RF field.Annex A discusses the sensitivity of EED and their firing circuits.

    1.1.3 To a large extent the sensitivity of EED to extraneous RF fields can be minimized byintrinsic design characteristics, screening and specialized packaging. However, there are anumber of circumstances, notably when EED are being transported or handled as a sub-systemunpacked, or being tested when they are particularly vulnerable to inadvertent initiation.

    1.1.4 The purpose of this chapter is to promote an increased awareness of the potentialdangers of operating equipments that produce a RF field in the vicinity of EED among agenciesinvolved with the storage, processing, movement and use of such devices. It includes requirementsand advice on the statutory and departmental regulations to be observed and the basicprecautions, which should be taken.

    1.2 Statutory Requirements

    1.2.1 Under existing legislation there is no single statute covering mandatory precautions to betaken when operating equipments producing a RF field in the vicinity of EED. The EU PhysicalAgents (EMF) Directive will introduce such legislation but implementation has been postponed until

    2012. The Health and Safety at Work Act 1974, however, places a general responsibility onemployers and those persons in responsible positions to ensure the health and safety of bothemployees and non-employees, including members of the public, who may be affected by theiractions. The Duty of Care principle requires that the risk of any hazard being realised shall bereduced to As Low As Reasonably Practicable (ALARP). This chapter identifies procedures thatare designed to meet this principle.

    1.2.2 MOD regulations concerning exposure of personnel to non-ionising radiation are set outin JSP 375 Vol 2 leaflet 22 (Ref 1) and in JSP 392 (Ref 2). These should be consulted for detailedinformation and guidance on this aspect of radiation control. However, for information the currentguidance on reference levels for personnel exposure is set out in Tables 1 and 2 below.

    Frequency Field StrengthV/m

    Power DensityW/m2

    1 8 Hz 20,000

    8 25 Hz 20,000

    0.025 0.82 kHz 500/f (kHz)

    0.82 65 kHz 610

    0.065 1 MHz 610

    1 10 MHz 600/f (MHz)

    10 400 MHz 61 10

    400 2000 MHz 3f (MHz) f/40(MHz)

    2.0 300 GHz 137 50

    Table 1 Reference Level for Occupational Exposure

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    Frequency Field StrengthV/m

    Power DensityW/m2

    1 8 Hz 10,000

    8 25 Hz 10,000

    0.025 3 kHz 250/f (kHz)0.003 1 MHz 87

    1 10 MHz 87/f (MHz)

    10 400 MHz 28 2

    400 2000 MHz 1.375f (MHz) f/200(MHz)

    2.0 300 GHz 61 10

    Table 2 Reference Level for General Public Exposure

    1.2.3 Publications providing regulations, information and advice on the storage, movement andhandling of EED are to be found as indicated below:

    (1) NATO: AC 258 Manual on NATO Safety Principles for storage of ammunitionand explosives.

    (2) Single Service: Navy Dept: BR 2924. (Ref. 3)

    Air Force Dept: DAP 110A-0102 -1D (Ref. 4) and 1E.

    (3) Joint Service: JSP 800 Defence Movements & Transport Regulations

    JSP 800 Vol 4a Dangerous Air Cargo Regulations.

    (4) Def Stan: Defence Standard 59-114 Principles of Design and Use of ElectricalCircuits Incorporating Explosive Components. (Ref. 5)

    (5) British Standards: BS 6657/2002 Assessment of Inadvertent initiation of BridgewireElectro Explosive Devices by radio-frequency radiation - Guide.


    2.1 Factors Affecting Susceptibility

    2.1.1 Any length of wire forming all or part of the firing lines to an EED, when placed in a RFfield, will act as an aerial and pick up some energy from the field. An electromagnetic hazardwould exist if the circuit contained an EED, and the RF level was sufficient to induce a power/current that was in excess of the no-fire threshold (NFT)1power for the device.

    2.1.2 The amount of power fed to a connected EED will depend on the length andconfiguration of the wires and on the ratio of the source to load impedance of the firing lines andEED. However, unless firing circuits are properly designed sufficient power to fire many EED canbe picked up in substantially lower RF field strengths than those experienced during some parts oftheir service life. The ability of a circuit to pick up power from a RF field can be increased when thecircuit is in contact with external conductors such as test cables, tools or fingers. Moreover, whenthe wires of an EED are separated they may form a more effective dipole antenna and provide anoptimum impedance match to the EED giving maximum transfer of power to the EED from theradiation source.

    2.1.3 For these reasons, EED separated from their parent system or in systems opened up formaintenance/test are regarded as less safe than when installed into the system as intended by thedesigner.

    1The no fire threshold power is defined as the power required to produce a 0.1% probability of fire at the

    95% single-sided lower confidence limit when applied to the EED for a time which is long compared with thethermal time constant () of the device, (i.e. >10 ).

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    2.1.4 The use of ammunition containers e.g. H83 and A480 should NOT be considered toautomatically provide sufficient attenuation for EED in isolation or EED contained in non-metallicsystems that are not adequately protected.

    2.2 EED Testing for Susceptibility to EM Radiation

    2.2.1 All complete explosive systems containing EED, which are intended for service use,should be assessed for their susceptibility to RADHAZ. The assessment may be theoretical,based upon the principles in Def Stan 59-114 (Ref 5) (ex OB Pillar Proceeding P101(2)), or apractical trial conducted at a specialist site.

    2.2.2 The assessments should cover the susceptibility of EED during preparation, testing,storage and transportation, loading and when loaded to the launcher/platform. These activities areoften identified by the categories shown in Table 3:

    Categories Activities1 (Dis)assembly of weapons/stores and testing of sub systems by personnel or

    machine generally in defence munitions organisation sites.

    2 Testing of all up weapons/stores in test houses or along side/on board

    3 Storage and transportation of weapons/stores in approved packaging. (Note:Approved packaging is that identified in the ESTC item listing.)

    4 Storage and transportation of weapons/stores not in approved packaging; orwhilst handling, assembling, loading/unloading to platform e.g. vehicle, gun,aircraft or launch platform.

    5 Weapon/stores loaded to its platform/launcher for its intended use (e.g. to aircraftor in its launcher).


    2.2.3 The assessments generally relate to the Minimum Service RF Environment (MSRFE)defined in Def Stan 59-114.

    2.2.4 The results of RF susceptibility assessments in terms of maximum safe field strength orpower density in various frequency bands are published in BR2924 Vol 2 (Ref 3) for naval systemsand many Embarked Military Force items and in DAP 110A-0102-1D (Ref 4) for aircraft systems.Individual system A&ER pamphlets provide safe distance information for land systems where theyare not cleared to the MSRFE.

    2.2.5 Where no data is published the worst case susceptibility curves at Annex A Figure 2 maybe used or guidance can be sought from Defence Ordnance Safety Group (DOSGST3).

    2.3 Minimum Separation Distances from Radio Frequency Sources for Weapon/StoresContaining EED

    2.3.1 A wide range of equipment emitting RF fields is employed in Service and civilenvironments. These include broadcast transmitters, communication radios, RF data links, mobilephones, satellite communications, radars, security scanners, remote controls, measurementsystems and computer wireless links. These contribute to an increasing level and spread in the RFenvironment and all must be considered when making RADHAZ assessments.

    2.3.2 In some instances this means safe distance restrictions will be required. In particularEEDs/weapons being handled and weapons under preparation, test or maintenance will frequentlyrequire procedural controls to ensure they remain safe.

    2.3.3 The magnitude of a RF field decreases with increasing distance from the source. Thehazard area for transmitters using omni directional or rotating antennae is often defined as a

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    spherical or right-cylindrical volume centred on the transmitter. For transmitters that have fixeddirectional beams radiating predominately in one direction (e.g. a satellite tracking system) thehazard area is mainly in the direction of the beam.

    2.3.4 The safe distance from Service transmitters for many EED systems, whose susceptibilityis known, can be determined by the use of the calculation method shown in Annex A. This requiresknowledge of the item susceptibility and the RF transmitter parameters. Data on these for manysystems is published in References 3 and 4. For radio systems with known power outputs asimplified procedure is outlined in Annex A. If the data required is not known advice should besought from DOSG ST3.

    2.4 Storage and Transport

    2.4.1 EED are encountered in a variety of configurations between their manufacturing stageand their ultimate use or disposal. These configurations range from trade packaging in bulk,Service packaging and sub packages and installation in munitions, to various stages of separateand exposed states that occur in processing and training.

    2.4.2 It is important for users to understand how these configurations can influence the basicprecautions to be adopted. Transportation and use precautions should also include measures to becovered in emergencies from straightforward vehicle breakdowns to accidents involving fire and/orcasualty evacuation.

    2.5 Storage & Processing Considerations

    2.5.1 Building materials are generally ineffective in affording significant EM protection for EED.Most structures provide no transmission loss from frequencies below 1 MHz but many providesome protection in the form of reflection loss if the polarisation and angle of incidence of the EMenergy happens to be favourable, although this is rare.

    2.5.2 For all practical purposes it should be assumed that the field strength that exists inside abuilding is the same as that of any external field. However, if the attenuation of EM radiation,which is provided by a specific building or room, has been determined (for all conditions ofdoors/windows being opened/closed) then this may be used to determine safe distances fromsources of EM radiation.

    2.5.3 EED and systems containing EED should only be stored/processed in licensed depotand unit storage and process areas. Siting of these areas should take account of:

    (1) The susceptibility of the EED or munitions containing EED during storage or processing asappropriate.

    (2) The proximity and radiated power of fixed transmitters in the area.


    3.1 Introduction

    3.1.1 In depots where weapon processing is being undertaken susceptibility levels may be attheir lowest and it is necessary for authorities to understand more fully the RF environment inwhich the work is being carried out and the interaction with the system firing circuits. Theenvironment will depend on local transmitters both on-site and in the local area.

    3.1.2 Transmitters outside the ESA perimeter. Outside the ESA and at least 100 metres froma processing building, radios with a power output of 50 watts or less with no significant antennagain can be safely used. For higher power radios or radars or shorter distances an assessmentwill be required to determine the possible field strength in processing areas. For some very highpower broadcast transmitters, air traffic control radars or military radars this may requireknowledge of their location out to distances of 3 km. The aim should be to ensure that the field

    strength at any frequency is less than the value shown in Fig 2 of Annex A. For major UK depotsDCSA DCTO-CM RSP have agreed to inform relevant responsible persons of new proposals for

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    significant RF installations within 3 km. This group should be contacted first concerning localemitters but where questions remain advice may be sought from DOSG ST3.

    3.1.3 Transmitters inside ESA. There are a number of portable radios (both hand-held andmanpack) in service or being used by contractors/site personnel during maintenance andmovement periods and it is likely that they will become more widely used. The use of managementradios, data links and RF tags/Wi-Fi etc. is also becoming more common.

    3.1.4 In the past, under the ALARP principle, there has been a blanket ban on the use oftransmitters within an Explosive Storage Area (ESA) unless specifically approved by DOSG ST3.With the increase of requests for advice on mobile transmitters for security and tracking reasonswithin ESA and with the advent of Wi-Fi/Bluetooth transmitters in computers and data links (whichmay be required for use inside process/storage buildings) there is a need to revisit this blanketban.

    3.1.5 The owner/managers of the site must therefore assess all RF transmitters to be used inthe vicinity of an EED, or stores containing an EED, for their potential RADHAZ. DOSG ST3 cangive specific advice where required. The paragraphs below set out the rules for transmitters insideESA and licensed buildings:

    (1) No deliberate RF transmitters of any power are to be allowed inside an ESA unless theyare essential for an activity that is taking place there.

    (2) Portable radios, personnel communication equipment, mobile phones, personal electronicdevices (PED) or data communications transmitters may be used inside an ESA andexternal to licensed buildings subject to the requirements of paras 3.1.6 and 3.1.7 beingmet.

    (3) No deliberate RF transmitters are to be allowed inside an explosives building unlessmeeting the requirements set out in para 3.2 below or specifically agreed by DOSGST3.

    (4) Assessments shall include safe distance calculations for the transmitters - portable orfixed.

    (5) The minimum safe distance for the use of any transmitter in the vicinity of an EED, nomatter what the susceptibility of the explosive nature, shall be 2m even if calculation showsit could be less (unless covered by the rules in para 3.2).

    (6) The safe distance applies equally to the use of transmitters in vehicles transporting EED,unless a relaxation has been applied for from the relevant IE who will seek advice fromDOSGST3.

    (7) Only ATEX certified transmitters classified safe to the relevant standard may be used inareas where an explosive atmosphere (gas/dust) may exist.

    3.1.6 For transmitters within an ESA but external to a processbuilding a generic worst-caseassessment has to be undertaken. Only essential transmitters should be installed within or takeninto an ESA but those that meet the rules below may be allowed without recourse to DOSGST3.

    (See also sub paras (1) & (2) below.)(1) All transmitters with a power output of 1 W, with an aerial gain of 3 dB, across the

    frequency spectrum are acceptably safe at a distance of 10m from the exterior of thebuildings.

    (2) All transmitters with a power output of 5 W, with an aerial gain of < 3 dB at a frequency

    of > 400 MHz are acceptably safe at a distance of 5m from the exterior of the buildings.

    3.1.7 Within an ESA and external to storage buildings where EED initiated items are onlystored in their approved ESTC containers (i.e. ordnance not unpacked, handled or worked on)transmitters with a power output of 25 W, with an aerial gain of 6 dB, across the frequencyspectrum are safe at a distance of 2m from the exterior of the buildings. Due to the possibleproblems with ensuring that all items remain packed at all times the use of radios at this power

    level shall only be permitted where absolutely essential and where strong controls are in place and

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    can be assured to be in place for the lifetime of the transmitter. Where there is doubt the safetydistances and power levels of para 3.1.6 above shall be applied.

    3.1.8 For all other transmitters a safe distance calculation shall be carried out as shown inAnnex A and the relevant distance imposed.

    Notes: (1) Transmitter power is to be taken as maximum the set is capable of emitting not

    a level which may be operator or software controlled.

    (2) By convention distances rounded up to 2, 5 or 10 m

    (3)The above safe distances shall also be maintained between the transmitter andESA transit routes.

    3.2 Inside Explosive Licensed Buildings

    3.2.1 Internal to Storage/Processing Buildings. Where transmitters are essential for the operationwithin a building (e.g. for reading RF tags or data loggers or for laptop Wi-Fi connectivity) the safedistance from explosive stores containing EED shall be calculated as set out in Annex B.

    Regardless of the distance derived no transmitters with an Effective Isotropic Radiated Poweroutput in excess of 1W shall be permitted inside an explosive process building or 2W in a storagebuilding. Prior to deployment of any transmitter approval should be sought from the relevant IE andthe calculations should be checked by DOSGST3. Strict controls shall be put in place to ensurethe safe distances are always maintained. Where multiple transmitters are required in a building(e.g. for RF tags/loggers) advice shall always be sought from DOSG ST3.

    3.2.2 The Bowman Personal Role Radio (PRR) has been assessed as being safe for use bypersonnel handling in-service explosive items. No further control is therefore required for themexcept in process areas where the rules of Annex B should be applied and the normalrequirements for CAT A, B and C areas shall be followed.

    3.3 Mobile Phones and Pagers

    3.3.1 Use of mobile phones and pagers must be controlled in the vicinity of munitions. As theirpower output is unpredictable and can be well in excess of 1W. Mobile phones and pagers shallNOT be used:

    (1) In explosive storehouses (ESH) / potential explosion site (PES) / magazine/ weaponstowage areas/explosive process buildings.

    (2) Close to ordnance under preparation.

    3.3.2 Subject to the above, essential mobile phones and pagers are permitted to be used inother areas provided that:

    (1) Only standard handheld phones/pagers are used.(2) Minimum separation distances as calculated in accordance with paras 3.1.6 and 3.1.7 or

    Annex A are adhered to.

    (3) Explosive vapour/dust hazards do not exist.


    4.1 Introduction

    4.1.1 It is not practicable to achieve a safe EED environment during transportation through theobservance of calculated safe distances. For this reason, all EED and systems containing EED

    offered for transportation should be assessed as safe to the Minimum Service RF Environment forsea and air transportation or a field strength of at least 200 V/m (~100 Wm -2) at all frequencies for

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    road transportation. (N.B. Any area around a transmitter where the field strength may exceed thelevels shown in Table 2 should not be accessible to the general public.)

    4.1.2 Service EED and systems containing EED which have not been cleared to an EMenvironment of 100 Wm-2 or the MSRFE (as appropriate) must be protected during transit byenclosure in a metal box or by approved materials providing sufficient screening. Specificinstructions on munitions incorporating EED which are either cleared or not cleared fortransportation with respect to RF protection are to be found in Service publications discussed atparagraph 2.2.4.

    4.1.3 Where the munitions are required to be closer than a minimum of 2 m from a vehicletransmitting antenna advice should be sought from DOSG ST3. Dependent on the power output,frequency and cable routing this may in some cases be reduced to 0.2 m for systems assessed assafe in the MSRFE.

    4.1.4 When it is considered necessary to transport systems containing EED of unknownsusceptibility, the worst case susceptibility curve at Figure 2 of Annex A may be used. Allpersonnel engaged in the carriage of such articles should be aware of RF hazards and observeconsignors instructions fully. Note should be made of any special instructions coveringloading/unloading/handling when EED are most vulnerable to EM radiation.

    4.2 Anti Theft Tracking Devices

    4.2.1 Vehicle tracking devices of various types and fulfilling various functions are now commonplace on vehicles used not only by contractors but also on a variety of MOD vehicles. Thesetracker systems are no longer used purely for tracking stolen vehicles but are more generally usedto monitor vehicle movements as well as driver profiling. Such tracker systems are often presentwithout the drivers knowledge and hence the type and function of such systems are known only tothe organisation undertaking the vehicle monitoring function. As a result of this increase in use andfunction of vehicle tracker devices a number of different systems are now commonly used andwhilst all utilise GPS for vehicle positioning various methods of communicating between the vehicleand central monitoring facility are used (eg. GSM, VHF & UHF).

    4.2.2 Vehicles carrying tracker devices shall not be taken into explosives buildings except inspecific areas identified for loading/unloading of packaged (or aircraft prepared) munitions or withinan appropriately licensed explosives building for overnight or short period parking as permittedwithin the constraints of the explosive licence (not applicable to EOD vehicles/garages). The safedistances as advised in Table 4 should be observed for the relevant state of the munition(s).Where the 10m safe distance from damaged/disassembled stores is not practical in particularestablishments DOSG should be provided with the list of weapons which may be involved todetermine if this distance can be reduced from the worst case value. Where a vehicle has beeninvolved in an accident and its explosives contents are damaged (or potentially damaged) thenadvice should be sought from DOSG if practicable.

    PackagedSafe Distance


    UnpackagedSafe Distance


    Damaged ordisassembledSafe Distance


    0.25 3 10

    Table 4 Safe Distances to be Observed

    4.2.3 Note that for stores which are in a packaged condition on a vehicle the transmit antennashould not be within 0.25 m of any electrically initiated item. It is the responsibility of the vehicle

    user and the vehicle supplier to ensure that the location of the transmit antenna is identified so thatthe distance to any explosives can be determined.

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    4.2.4 The term Packaged in this instance means the explosive item is contained within itsESTC approved packaging. This equates to Category 3as described in Table 3.

    4.2.5 The term Unpackaged in this instance means the explosive item has been removedfrom its ESTC packaging but remains in an assembled or all-up-round state or forms part of acomplete assemble. This is also applicable to items installed on a platform. This equates toCategory 4(or Category 5for items installed on a platform) as described in Table 3.

    4.2.6 The term Damaged or Disassembled in this instance means the explosive is not in itsESTC packaging and is physically damaged or is broken down for test and/or assembly purposes,ie. typical activities undertaken within a processing facility. This equates to Categories 1 and 2asdescribed in Table 3.

    Emergency Transportation Procedures

    4.2.7 In the event of an incident/accident during transportation of munitions, items which do notnormally present a high RADHAZ risk may become acutely vulnerable if there is damage to theirinherent protection, i.e., structural or packaging. Pending a detailed inspection the undermentioned restrictions on RF transmissions in the immediate vicinity should be imposed


    (1) No RF transmission is to be allowed within a radius of 10 metres from the EED.

    (2) Emergency services using radios with EIRP greater than 5 watts should not transmit within50 metres of the damaged equipment. (EIRP = Effective Isotropic Radiated Power)

    (3) Drivers and/or escorts in vehicles transporting EED should be issued with the Notice toCrews of Road Vehicles carrying Military Explosives including Ammunition (example, seeJSP 445) that details actions to be taken in the event of an incident/accident.


    1 JSP 375 Health and Safety Handbook Vol 2 Leaflet 22 Safety in the Use of ElectromagneticRadiation

    2 JSP 392 Radiation Safety Handbook3 BR2924 Radio Hazards in Naval Service Volume 24 DAP110A-0102-1D 3rdEdition dated Nov 03 & -1E 2ndEdition dated Nov 005 Def Stan 59-114 Principles of Design and Use of Electrical Circuits Incorporating Explosive

    Components.6 DOSG Div Note 77/2005 dated 07/03/057 DOSG Div Note 75/2005 dated 16/02/05

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    CHAPTER 24






    1.1 Introduction


    2.1 Main Types of EED in Use and Their Properties2.2 EED Sensitivity Thresholds2.3 Transmitter Characteristics2.4 Safe Distance Calculations

    Table Page1 The Minimum Service Radio Frequency Environment 22 Example EED No Fire Thresholds 33 Quick Reference Minimum Separation Distance (metres) for Radios up to 1GHz 4


    1.1 Introduction

    1.1.1 An EED can be a component of a munition system or subsystem having no separateexistence during the munition life cycle save during manufacture, refurbishment or disposal.Alternatively an EED may be fitted into a munition system in the field such that it is stored andtransported as a separate item, (e.g. an electric detonator fitted to a demolition charge).

    1.2.1 The energy to initiate an EED (either directly or via coupling electronics) may be from theintended source or accidentally by pick-up from RF transmitters.

    1.3.1 Radio and radar transmitters throughout the world operate over a wide frequency

    spectrum. The RF environment in which service equipments should be designed to remain safe(and in some cases operate) is given in Def Stan 59-114. This is often known as the MinimumService RF Environment (MSRFE). (Note this has replaced STANAG 4234 since recent evidencehas shown the need to re-define the levels that may be experienced in some situations. The newlevels will be applied to new design/procured equipments only and assessments to the previouslevel remain valid). However not all systems/EED meet these levels in all operationalconfigurations and some transmitters may exceed these environments at close range.

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    Field Intensit ies

    STANAG 4234 Def Stan 59-114

    FrequencyVm-1 Wm-2

    (average)Vm-1 Wm-2


    200 kHz - 525 kHz 300 200525 kHz 2 MHz 200 200525 kHz - 32 MHz 200 20032 MHz - 150 MHz 10 30150 MHz - 225 MHz 100 80225 MHz - 400 MHz 50 100400 MHz 790 MHz 50 50

    790 MHz - 1GHz 1000 1501 GHz 2.5 GHz 1000 1000

    2.5 GHz 4.5 GHz 1000 2400

    4.5 GHz 6.0 GHz 1000 500

    6.0 GHz 8.0 GHz 1000 1500

    8.0 GHz 12 GHz 1000 1500

    12 GHz 18 GHz 1000 1500

    18 GHz - 40 GHz 100 500

    Table 1 The Minimum Service Radio Frequency Environment


    2.1 Main Types of EED in Use and Their Propert ies

    2.1.1 Those EED in current and envisaged service use can be divided into 2 groups, low

    voltage and high voltage types. In general, these can be sub-categorised into 3 broad types:(1) Low voltage devices with long thermal time constants (typically 10ms - 50ms) such as

    bridgewire (BW) devices that are known commonly as power sensitive.

    (2) Low voltage devices with short thermal time constants (typically 1s-100s) such as FilmBridge (FB) and Conducting Composition (CC) which are known commonly as energysensitive.

    (3) High voltage devices with a secondary explosive such as Exploding Bridgewire (EBW) andExploding Foil Initiator (EFI) devices which require a fast, high voltage discharge pulse toinitiate them. These are commonly known as HV devices.

    2.2 EED Sensit ivity Thresholds

    2.2.1 Power sensitive devices tend to integrate transient energy and, in the case of repetitivelypulsed radars will respond to mean or average power levels. LV energy sensitive devices tend torespond to the peak power level of an electrical transient/pulse and pulse stream (e.g. pulsedradar) and this must be taken into account when determining their susceptibility. HV devices aregenerally considered to require such a specialised, fast rising pulse that accidental initiation from aradio or radar field is not credible and assessments are against accidental dudding.

    2.2.2 Whilst the above groups describe the salient characteristics of each type of EED itshould not be inferred that they react exclusively to either power or energy impulses. Indetermining hazard thresholds (known as No Fire Thresholds (NFT))bothtypes of reactions areconsidered. To illustrate the results a typical BW EED (igniter Type F53) and a typical CC device(type M52) NFT figures are shown in the following table.

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    EED ResistanceRange(Ohms)






    Igniter Type F53 0.9-1.6 130 2.3 18

    M52 CC Igniter 1k 1.2M 14 0.0022 0.157

    Table 2 Example EED No Fire Thresholds

    2.3 Transmitter Characteristics

    2.3.1 There are a number of radios and data communication links in service or being used bycontractors/site personnel for maintenance and operations and it is likely that use of the RFspectrum will continue to increase.

    2.3.2 RF transmitters should not be used in areas of munition handling or in the vicinity ofmunition routes when stores are being handled, during loading/unloading and close to storesloaded to a launcher without proper consideration of their safety. Some simple worst-case safetydistance rules for transmitters are given in the main section of this chapter and these should be

    applied if possible. Where these rules are not capable of being met or where more detailedassessments are required a safe distance shall be calculated and applied as shown below.

    2.3.3 Transmitters in Service use are listed in Single Service publications produced under RN,Army and RAF arrangements. The Navy (Ref 3) and the RAF (Ref 4) publications present fieldstrength against distance graphs for high power microwave transmitters. Where these graphs arenot available or do not show the relevant system the following information is the minimum requiredto calculate their field strengths:

    (1) Type of aerial (directional or omni-directional).

    (2) Mean and peak power fed to the transmitter antenna (watts).

    (3) Frequency or frequency band of the transmitter.

    (4) For a directional antenna the antenna gain.2.3.4 This information is generally available in the equipment handbooks or from theappropriate agencies/manufacturer.

    2.4 Safe Distance Calculations

    2.4.1 It is then necessary to obtain the susceptibility level (at the transmitter frequency) of therelevant store(s) or use a worst case assessment. Susceptibility levels for most in-service storesare listed in Refs 3 & 4 or for many Army systems in the relevant AESP. Once susceptibility levelshave been ascertained, it is then possible to translate this information into minimum separationdistances (hazard area) from radio and radar transmitters. There will generally be a number ofminimum distances to allow for the type of activity being undertaken.

    2.4.2 Where the transmitter information and the susceptibility of the EED is known then theformula below may be used to derive a safe distance.



    4= metres


    D is safe distance in metres

    P is average transmitter power in watts

    G is antenna gain (as a linear number NOT dB)

    S is susceptibility level of EED/store in W/m2(at the frequency of the transmitter)

    2.4.3 If the EED is an energy sensitive device then a multiplication factor needs to be includedto take account of the transmitter pulse characteristics and the EED thermal time constant. These

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    calculations become relatively complex and advice should generally be sought from DOSG ST3.The method is however documented in references 3 & 4 for those who wish to undertake their owncalculations. (Note: this factor is generally only relevant for microwave pulse transmitters such asradars). The only systems in service at time of publication of this JSP that have LV energysensitive EEDs are: Aden, Mauser and Phalanx cannon rounds, TVE (for 120mm gun) and the 4.5Naval Shell. References 3 & 4 contain full susceptibility data for these items.

    2.4.4 Alternatively for typical radio systems the lines in Figure 1 may be used to determine thesafe distance for an EED with a known susceptibility.

    2.4.5 Again for radio systems only, where the transmitter information is known, but thesusceptibility of the munition is unknown, reference may be made to Table 3 to determine the safedistance from the most sensitive store being used and handled in its normal service configuration(including handling of EOD detonators). Where a store has been damaged or dismantled the safedistance should be calculated using the safe power density derived from the red line on the graphat Figure 2. The distances can be used for frequencies up to 1 GHz but above about 60 MHz thedistances will be pessimistic and more realistic figures will generally be found by calculation usingthe graph at Figure 2 to determine the susceptibility of a worst case undamaged store (red line) ora worst case damaged/disassembled store (blue line).

    2.4.6 The safe distances determined under this publication are subject to any over-ridinglimitation laid down elsewhere for the protection of personnel against the biological effect of RFradiation.



    1 W 4 W 6 W 10 W 15 W 25 W 30 W 50 W


    5 m 10 m 13 m 17.5 m 20 m 26 m 28 m 36.5 m



    6.5 m 13 m 16 m 20.5 m 25 m 32.5 m 35.5 m 46 m


    7.5 m 15 m 18 m 23 m 28 m 36.5 m 40 m 51.5 m

    HIGH GAIN(5)

    10 m 18.5 m 22 m 29 m 35.5 m 46 m 50 m 65 m

    Table 3 Quick Reference Minimum Separation Distance (metres) for Radios up to 1 GHz

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    1 10 100 1000

    Distance (m)

















    Field StrengthV/m




    21 2 3 4 5 6 7 8 9 10 11 12 13 14

    Antenna TRANSMITTER POWER in Watts

    Gain dB 1 5 10 15 20 25 30 50 100

    0 1 3 4 5 6 7 8 10 12

    2 2 5 8 0 11 13

    3 2 4 6 8 9 10 11 12 13

    5 3 5 8 10 11 11 11 13 14

    6 3 6 9 11 11 13 13 14 14

    4 7 9 1

    Fig. 1 RF Power Density Hazard Graph for Radios (Frequencies from 60 to 500 MHz)

    Note: 1 Determine appropriate line from table using transmitter power and antenna gain.Read across from EED susceptibility to relevant line and down to see safe distance.

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    0.1 1 10 100 1000 10000 100000

    Frequency MHz



    Worst Case In-service store(being handled)

    Figure 2: Worst Case Susceptibility for In-service Stores

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    CHAPTER 24







    Table Page1 Transmitter parameters with minimal safe separation distances 2


    1.1 As noted in the main body of this chapter new applications for modern technology aredriving a requirement for a variety of wireless transmitters to be used inside explosive storage andprocess buildings. Such applications range from data loggers, environmental monitors and Wi-Fienabled laptops through to readers for loggers/recorders and data links to remote control positions.Many such applications are becoming essential for the operation of a facility and so regulationsunder which the transmitting devices may be permitted inside a building are required.


    2.1 Individual radio transmitters may be permitted inside an explosive storage and processbuilding subject to the following:

    (1) No transmitter may have an Effective Isotropic Radiated Power (EIRP) output of greaterthan 1 Watt for use in a process area or 2 watts for use in a storage area. (Note EIRP =output power x antenna gain).

    (2) Unless agreed in advance by DOSG ST3 items to be placed inside weapon storagecontainers shall have an EIRP < 50 mW and shall operate at a frequency > 2000 MHz.

    (3) A worst case safe distance shall be calculated for each item as shown below and the itemshall carry a label clearly showing this distance.

    (4) Portable transmitters inside a process area shall not require a safe separation distance ofmore than 1 metre, as determined by the method outlined below. Items requiring a greatersafe separation distance shall be permanently fitted and a full assessment carried out toensure the safe distance will always be maintained from all electrically initiated stores.

    (5) The equipment shall meet the same electrical standards as required by other itemsrelevant to the Category of the building (see Chapter 8).

    (6) Where multiple transmitters are required in a building (e.g. for data loggers or RF tags)advice shall always be sought from DOSG ST3.

    2.2 Transmitters with an EIRP of 5 mW or less at any frequency do not require a safeseparation distance. Above 400 MHz transmitters with greater power output can be permitted with

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    only a minimum safe separation distance. (Note: Transmitters should not be permitted to touch anEED or firing line.) These levels are shown in Table 1.

    EIRP mil liWatts Frequency Safe Separation Distance

    < 5 Any Near touching

    5 EIRP < 10 400 MHz 10 cm

    5 EIRP 50 2000 MHz Near touching

    Table 1 Transmitter parameters with minimal safe separation distances

    (Note: Near touching is defined as in close proximity to a firing circuit or EED but the transmittercase or antenna should not touch the wires or EED.)

    2.3 For transmitters with an antenna that is not omnidirectional (i.e. gain >1.6 dB) the safedistance will need to be determined by measurement and DOSG advice shall be sought on themethod to be used. For all other transmitters a safe separation distance shall be determined usingthe method set out below.

    (1) Establish power reduction ratio from transmitter output power (PT) to maximum allowablepower received (PR). If PR / PTis less than 0.04 use the formula at paragraph 2.4 tocalculate safe distance. (For PRuse a value of 2.5mW)

    (2) If PR / PTis greater than 0.04 use the graph at Figure 1 look up spacing required (inwavelengths) for PR / PT.

    (3) Calculate safe separation distance in metres equivalent to this value using formula below:

    Safe separation distance = spacing (wavelengths) x 300 / f metres

    Where f = frequency in MHz

    (4) Where the safe separation distance is less than 0.02 m (2 cm) it can be reduced to neartouching.

    2.4 Where PR / PTis less than 0.04 the safe distance can be calculated using the formula:

    D = 2 x x SQRT(PTx GT)

    Where D is safe separation in metresPTis transmit power (watts)GTis transmit antenna gain (as a ratio not in dB)

    2.5 It is important for this assessment that the values used for PTand GTare the maximumpossible for the family of devices. They should be determined by measurement rather than frommanufacturers claims. If no measurements are available a factor of at least 3 dB shall be added toa specification figure. For Transmitters in which the power output is controlled manually or bysoftware the maximum power capability of the RF circuit shall be used in all calculations andmeasurements. Where the distance determined is deemed to be not practical in use ameasurement using the method defined in Ref 12shall be performed. The specialist antennasrequired may be constructed by a competent test house (after consultation with DOSG ST3) orDOSG ST3 can recommend companies capable of making the measurements. An alternative testmethod in which the E field is measured by use of a 3-axis probe may be used at frequencies

    2Thales Report RHD 1999. Test Method for Measuring the Hazard from Low Power RF Devices. April 2007

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    above 100 MHz. DOSG ST3 should be consulted on this method. The distance at which the E fieldfalls below the level shown in figure 2 shall be taken as the safe separation distance.

    2.6 The distance determined must be clearly displayed on the transmit device and proceduresput in place to ensure this distance is maintained from any EED.




    0 0.1 0.2 0.3 0.4 0.5 0.6

    Spacing (Wavelengths)



    Figure 1: Power Transfer Ratio vs Spacing

    Figure 2: Maximum Electric Field vs Frequency

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    Table Page1 Safe Distances for ESTC Approved Packaged Stores Cleared to MSRFE 32 Safe Distances for Handling Undamaged Stores 53 Worst Case Safe Distances for Undamaged Stores/EED for Radios up to 1 GHz 5


    1.1 The guidance contained in this Annex is aimed at operational scenarios and is principallyrelevant to army deployments since the regulations concerning RN ships and RAF bases are

    contained in BR 2924 Vol 2 and DAP110-0102-1D and 1E respectively.

    1.2 This Chapter does not include the precautions to be taken when operating, connecting orloading weapons/stores containing EED. Such regulations are contained in the user handbook orare issued by the user arm concerned (see references in para 1.1 for RN and RAF use).

    1.3 No user knowledge of weapon susceptibility or transmitter parameters is assumed. Furtherinformation is available on this from the local Explosives Technical Authority (see Chapter 1 AnnexB). In addition Annex A to this chapter contains the method for calculating safe distances forsystems including worst case calculations when necessary.

    1.4 In all cases of difficulty, advice may be obtained from the Ammunition Technical Officer

    (ATO)/ (RN, RAF or Civilian Equivalent) or for specialist advice consult DOSGST3.2 GENERAL

    2.1 Relatively little power is required to fire many EED and they will normally respond to eithera direct or alternating current signal. EED will therefore respond and fire when sufficient EM energyis coupled into the firing circuit to which they are connected even when there is no power supply.This energy may radiate from an antenna of a radio, radar or other transmitter or be generated asa transient from other electrical equipment.

    2.2 The protective switch, which prevents the initiation of an EED by the firing circuit until thedesired time, does not prevent pick-up of rf energy on the wiring between the switch and the EED.Moreover, if the switch is electronic it may not provide a break to energy at microwave frequencies.

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    2.3 Energy from the EM environment can enter a store through non-conducting covers and anydiscontinuity in its skin (e.g. inspection windows, GRP casings, joints). The degree of screeningprovided by packaging will depend on the conductivity of the material used and the presence ofslots or joints for lids etc.

    2.4 The use of ammunition containers e.g. H83 and A480 should NOTbe considered to

    automatically provide sufficient attenuation for EED in isolation or EED contained in non-metallicsystems that are not adequately protected although they do provide adequate shielding in manysituations relevant to army operations.

    2.5 In general, stores containing EED are more susceptible to EM energy pick-up whenremoved from their container and when being handled, loaded and unloaded into/from weapons orplatforms.

    2.6 The ability of a firing line to pick up sufficient energy to cause an EED to operate dependson many factors. These include the electrical characteristics of the EED, the nature of the firingline, its length and geometry, the EM field strength and the frequency transmitted. The EM fieldstrength is dependent upon the power output of the transmitter, the characteristics of the antenna

    system and the distance between the antenna and the firing circuit. In a large system it is not theposition of the EED that is important, but the position of the whole firing circuit in relation to the EMfield.


    3.1 All in-service stores containing an EED are assessed for their susceptibility to RF whenpackaged in their ESTC approved container, when being handled and where relevant when loadedto a weapon launcher. Such assessments attempt to demonstrate clearance to the MinimumService RF Environment (MSRFE) which is deliberately set at a high level.

    3.2 At all stages in their life it is essential that stores containing EED are not exposed to a RF

    environment exceeding their safe limit. For items in their ESTC approved packaging and clearedto the MSRFE there are only a few transmitters in land service use which require safe distancerestrictions. These are listed in Table 1. (Note, however, that such radios are prohibited from usein explosive storage buildings and prior approval is required for radios in explosives storage areas(ESA)).

    3.3 Even where no restrictions are shown in Table 1 it is not good practice to place electricallyinitiated ordnance in close proximity to a transmitting antenna. A safe distance of at least 2m istherefore recommended as being the minimum that should be applied whenever practical.

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    Frequency Band Common Army Radio Types Safe Distance


    HF (1.5 30 MHz) TRC 521,D11/R230/234


    BOWMAN PRC 325, 327,

    VRC 328, 329


    VHF (30 225 MHz)

    Ptarmigan SCRA VRC 470


    Radio Relay C41/R222

    BOWMAN PRC 354, 355, 356,

    VRC 357, 358, 359



    (225 790 MHz)

    Radio Relay TRC471 TRIFFID I &II

    C50/R236, C70


    SATCOM V/UHF PSC 505, 510 3

    SATCOM (I Band) VSC 501, TSC 502 5*

    RADARS Rapier, Cymbeline, AN/TQP-37,LCMLR


    RADARS Mamba, Cobra 150*

    Table 1 Safe Distances for ESTC Approved Packaged Stores Cleared to MSRFE

    * These distances assume illumination by the main beam of the transmitter. Where this can beassured not to occur the distance may be reduced to 3m except for Cobra where 15m shall beapplied.


    (1) Where an in-service transmitter is not included a safe distance of 2m can be used for allradios with an output power of less than 25 watts. For all other transmitters a safedistance calculation must be done using data either in the relevant publication for the storeor in BR2924, DAP-110A-0102-1D/1E. In case of difficulty consult DOSGST3.

    (2) For vehicles fitted with radios and having designated stowage positions for electricallyinitiated ordnance, assessments are carried out to ensure that the nominated weapons willremain safe. The above distances do not therefore apply to such weapons and stowages.


    Jan 2013 Chap 24 Annex C

    4.1 During storage and transport all items should remain packed in their ESTC approvedcontainers. The safe distances noted in Table 1 shall be applied during storage and transport. Thedistances apply to radios fitted to a vehicle carrying the store, and to transmitters which may beencountered on route. (Note, however, that for service vehicles with fitted radios and designatedstowage positions individual assessments of RADHAZ safety are conducted during vehicle designto ensure they remain safe.) This is relevant whether movement is by land, sea or in the air but

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    see the publications discussed above for regulations for sea and air transport. For service and non-service radios, which may be encountered during transport on public roads etc, the personnelRADHAZ levels will be more restrictive. Packaged ordnance will therefore be safe unless takeninside a personnel RADHAZ boundary. Electrically initiated stores not packed in their ESTCapproved manner may be more susceptible. Individual system publications should containguidance where greater safe distances are required. Where this is not known the

    distances/precautions given below for handling should be followed unless further information isobtained.


    5.1 When stores containing EED are removed from their package, the susceptibility to EM pick-up may increase and larger safe distances may be necessary. Individual A&ERs should beconsulted for any restrictions imposed. Where these are not available, or there is doubt, worstcase distances from in-service radios are given in Table 2. These distances have been calculatedusing the maximum likely susceptibility for any undamaged store. For most stores this will be verypessimistic and where this creates a problem DOSGST3 should be consulted for detailed advice.It should be noted that the distances in Table 2 do not apply to radio or radar equipment

    associated with a store in its systems environment (e.g. guided missiles and their trackingequipment), nor do they apply to demolition firing circuits which have already been connected tothe detonator. In these cases the user arm concerned will issue instructions.

    5.2 In order to allow units to make their own assessments for management and other radioswhich may be in use locally the distances obtained from Table 3 below may be used. This requiresbasic knowledge of the radio concerned but again is based on pessimistic assumptions related tohandling an in-service detonator to calculate the minimum safe distance. These figures may beused at radio frequencies up to 1 GHz.

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    Frequency Band Common Army Radio Types SafeDistance(metres)

    HF (1.5 30 MHz) SR 718 U5, BOWMAN PRC 325, 327,

    VRC 322, 328, 329


    HF (1.5 30 MHz) TRC 521,SR D11/R230/234, SR D13/R234(2) 150

    VHF (30 225 MHz)

    SR PF85 PFX, SR EX PF85C, SR MX294,VRC 301, SR F494, SR FM914PM,VRC 390/391, GRC 391, CQP 813/833FRC 395 (TA4523L&H), FRC 398 (4525L&H)VRC 396 (TA4523L&H) PRC 397 (TA4523L&H)SR AN/ARC 340, SR AD 120, SR SRM 4515,SR STR 38, SR AN/ARC 44BOWMAN PRC 354, 355, 356, VRC 357, 358,



    VHF (30 225 MHz)Ptarmigan SCRA VRC 470, SR T404, SR T406Radio Relay C41/R222 100

    V/UHF(225 790 MHz)

    PRC 344/392, SR PF85 PFX, SR EX PF85C,SR MX 296, SR T414, SR F496, CQP 863,FRC 395 (TA4523U), VRC 396 (TA 4523U),FRC 398 (SRM 4525U), SR PTR 1751/170,


    V/UHF(225 790 MHz)

    Radio Relay TRC471 TRIFFID I & IIC50/R236, C70 50

    V/UHF PSC 505, 510, TRC 471 TRIFFID III,




    SATCOM (I Band) VSC 501, TSC 502 15

    RADARS Rapier, Cymbeline, AN/TQP-37, LCMLR 30

    RADARS Cobra, MAMBA 600

    Table 2 Safe Distances for Handling Undamaged Stores




    1 W 4 W 6 W 10 W 15 W 25 W 30 W 50 W


    5 m 10 m 13 m 17.5 m 20 m 26 m 28 m 36.5 m


    6.5 m 13 m 16 m 20.5 m 25 m 32.5 m 35.5 m 46 m


    7.5 m 15 m 18 m 23 m 28 m 36.5 m 40 m 51.5 m

    HIGH GAIN(5)

    10 m 18.5 m 22 m 29 m 35.5 m 46 m 50 m 65 m

    Table 3 Worst Case Safe Distances for Undamaged Stores/EED for Radios up to 1 GHz

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    5.3 Above 1 GHz the safe distances during handling for some in-service transmitters are givenin Table 2. Where these distances are not practical or the transmitter is not listed actualsusceptibility figures must be obtained from A&ERs or from DOSGST3 and the safe distancecalculated in accordance with Annex A.

    5.4 The Bowman Personal Role Radio (PRR) has been assessed by the DOSG as being safe

    for use by personnel handling in-service explosive items and so no further control is required forthem (except they are not suitable for use in flammable/explosive atmospheres and in magazinesand explosive storage buildings).