| Last updated date: | Reason for update: |
|---|---|
| 05 January 2023 | Updated to align with Regulations 2018 and minor editorial update |
1. Purpose
This document is provided to assist controlled persons to determine whether a radiofrequency (RF) source is classed as a controlled apparatus under the Australian Radiation Protection and Nuclear Safety Act 1998 (the Act). In particular, it clarifies conditions and defines terms used in Section 9 of the Australian Radiation Protection and Nuclear Safety Regulations 2018 (the Regulations).
2. Controlled apparatus
The Group 1 table in section 4 of the Regulations defines some of the types of RF emitting devices which are classed as controlled apparatus.
The following are examples of RF devices:
- a magnetic field non-destructive testing device
- an induction heater or induction furnace
- an industrial radiofrequency heater or welder
- a radiofrequency plasma tube
- microwave or radiofrequency diathermy equipment
- an industrial microwave or radiofrequency processing system
More explanatory examples of the above listed RF emitting devices can be found in Appendix 1.
Note: In section 44 (7) of the Regulations exempt dealings for the following RF emitting devices:
- radar equipment used for detection and ranging
- radiofrequency equipment used for communications
- Klystron
3. Criteria to be satisfied
Section 9 of the Regulations consists of two separate criteria, both of which must be fulfilled for the apparatus to be classed as controlled apparatus.
The first criterion paragraph 9(1)(b) concerns source emission. It is fulfilled if the apparatus produces non-ionising radiation that could lead to a person being exposed to radiation levels exceeding the non-ionizing radiation exposure limits. For RF the relevant standard referred to in section 4 is Radiation Protection Standard for Limiting Exposure to Radiofrequency Fields – 100 kHz to 300 GHz (RPS S-1). This document specifies reference levels which have been derived from the basic restriction levels. The reference levels have been chosen as they are based on quantities that are easy to measure and compliance with the reference levels will ensure compliance with the basic restrictions. See Appendix 2 for more details and extracts from RPS S-1.
Some of the apparatus (for example induction heaters) also generate electric and magnetic fields at 50/60 Hz. In this case the exposure limits referred to in section 4 are in the ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields (1 Hz – 100 kHz). See Appendix 3 for more details and extracts from the ICNIRP Guidelines.
The second criterion, paragraph 9(1)(c) is based on the accessibility of the source. Factors determining whether radiation above the exposure limits is accessible to persons have to be evaluated. The condition is fulfilled if excess levels of radiation are readily accessible to persons in any of the following situations:
- in the course of intended operations or procedures of the apparatus; or
- as a result of a reasonably foreseeable abnormal event involving the apparatus; or
- as a result of a reasonably foreseeable single element failure of the apparatus; or
- without the use of tools or other specialised equipment required to remove protective barriers or access panels.
The following procedure describes how to go through these two criteria to determine whether an RF emitting device is classed as controlled or not.
4. Radiofrequency (high frequency) and low frequency radiation
The part of the electromagnetic spectrum with high frequencies is in the range 3 kHz to 300 GHz and is referred to as radiofrequency (RF). The low frequency is in the range of 1 Hz to 100 kHz which include the 50/60 Hz electric and magnetic fields. The diagram below shows the divisions of the electromagnetic spectrum that are commonly accepted and will be used in this guide. Microwave (MW) frequency radiation is commonly used to denote a subset of RF radiation, typically at frequencies from 300 MHz to 300 GHz.
RF and MW radiation are forms of non-ionising radiation where individual photons are not energetic enough to break chemical bonds or remove electrons (ionisation). Ultraviolet, visible and infrared light are other forms of non-ionising radiation.
Figure 1: Electromagnetic spectrum with frequencies of some RF applications shown
Reference Documents
- Radiation Protection Standard for Limiting Exposure to Radiofrequency Fields – 100 kHz to 300 GHz (2021), ARPANSA Radiation Protection Series S-1 (RPS S-1).
The ARPANSA RF Standard sets limits for human exposure to RF EMR in the frequency range 100 kHz to 300 GHz. The Standard also includes requirements for management of risk in occupational exposure and measures for protection of the general public together with additional information on measurement and assessment of compliance. Extracts from this document can be found in Appendix 2.
- ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields 1Hz-100 kHz (2010), Health Physics 99(6):818-836.
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines are aimed at preventing the established health effects resulting from exposure to ELF EMF. The ICNIRP ELF guidelines are consistent with ARPANSA’s understanding of the scientific basis for the protection of the general public and workers from exposure to ELF EMF. Extracts from this document can be found in Appendix 3.
Definitions
Exposure limits – Elimit: are defined in terms of basic restrictions for occupational and general public exposure as specified in RPS S-1 and the ICNIRP Guidelines. Different exposure limits apply for occupational exposure and exposure to the general public.
Controlled apparatus (non-ionising) as defined in the Act: an apparatus prescribed by the regulations that produces harmful non-ionising radiation when energised.
Procedure for determining controlled apparatus
This procedure (as illustrated by the flow chart below) will assist you to determine whether your apparatus is controlled or not.
This procedure (as shown in the flow chart below) will assist you to determine whether your apparatus is controlled or not.
1. A prescribed apparatus that produces non-ionizing radiation that could lead to a person being exposed to radiation levels exceeding the non-ionizing radiation exposure limits. For example, if the apparatus is one of the devices stated in Section 1 Controlled apparatus.
2. If there is a reasonably foreseeable abnormal event that could lead to a person being exposed to radiation levels in excess of the maximum exposure level, as specified in RPS S-1 or the ICNIRP Guidelines and reproduced in Appendix 2 and Appendix 3, the apparatus is classed as controlled apparatus. Examples of reasonably foreseeable abnormal events are possible exposure during normal maintenance, easy overriding of an interlock, entry into exclusion zones etc.
3. If there is a reasonably foreseeable single element failure of the apparatus that would lead to a person being exposed to levels above the maximum exposure level, then the apparatus is classed as controlled apparatus. An example of this is a malfunctioning interlock.
4. If the apparatus is enclosed the possibility of removal of the access panels or protective barriers has to be assessed. If there is no enclosure, choose no, and go to the next step. If a person can be exposed to levels above the maximum exposure level when removing protective barriers or access panels that do not require the use of tools or other specialized equipment, the apparatus is classed as controlled apparatus.
5. Estimate the exposure level that a person could receive in the course of intended operations and procedures, ELop. The distance to the unit during intended operations should be estimated and the expected exposure level calculated or measured. The attenuation provided by any fixed shields should be taken into account.
Compare with the exposure limits (Elimit) as specified in RPS S-1 or ICNIRP Guidelines.
If ELop > Elimit then the apparatus is classed as controlled apparatus
If ELop < Elimit then the apparatus is not classed as controlled apparatus
Appendix 1: Examples of RF emitting apparatus
1. Induction heater
Definition: A heater that uses an induced electric current to produce heat.
Description: In an induction heater a conducting material is heated by induction of an electric current in the object to be heated. The resistance of the metal leads to heating. An induction heater consists of an electromagnet through which a high-frequency alternating current is passed. Heat can also be generated by magnetic hysteresis losses.
Induction heating provides a controllable and localized method of heating without contact between the heater and the components. Typical uses for induction heaters are heat treatment of metals, hardening of steel, annealing, bonding, curing and forging. A typical induction heater is shown below in Figure 2 and induction heating of a metal bar is shown in Figure 3.
Figure 2: Induction heater
Figure 3: Induction heating of a metal bar
[Source: Remarkable Machines Affordable Price | Superior Induction Company]
Operating frequencies range from 50/60 Hz to over 1 MHz. Induction welders and induction solders are types of induction heaters and are included in the above category.
2. Induction furnace
Definition: A furnace that uses an induced electric current to heat a metal to its melting point.
Description: An induction furnace uses induction to heat a metal to its melting point. The heating mechanism is the same as in the induction heater. Common metals that are melted are iron, steel, copper, aluminium and precious metals. Melting and mixing rates can be controlled by selecting and varying the frequency and power. A picture of an induction furnace is shown in Figure 4.
Figure 4: Induction furnace
3. Industrial radiofrequency heater
Definition: A heating device in which heat is generated through a radiofrequency field. Industrial signifies that the apparatus is not used for domestic applications.
Description: The frequency of operation of RF heaters is in the range 10 MHz – 100 MHz, with output powers up to 100 kW. Common frequencies are 13.56 MHz, 27.12 MHz and 40.68 MHz. These frequencies have been designated to prevent interference with communications equipment.
RF heaters are used to heat, melt, dry or cure dielectric materials (insulators or poor conductors that can be polarized by an applied electric field). Plastic, glue and rubber are electrical and thermal insulators and consequently difficult to heat using conventional methods. These materials are well suited for heating with an RF heater. This is in contrast to induction heaters (defined in the previous section) which operate at lower frequencies and are used to heat materials which are good conductors of electricity. RF heaters can be used in industrial drying processes and are then often called RF dryers.
4. Industrial radiofrequency welder
Definition: A heating device in which heat is generated through a radiofrequency field and the heat is used to weld the material. Industrial signifies that the apparatus is not used for domestic applications.
Description: The heating mechanism is the same in an RF welder as in an RF heater. The material (often plastic) is heated to its melting point and the work pieces are joined together. RF welders are sometimes called RF sealers. An example of a RF welder is shown in Figure 5.
Figure 5: Industrial RF welder
[Source: RF Sealers with Bar Welders | Custom Automation | Cosmos and Kabar (cosmos-kabar.com)]
5. Radiofrequency plasma tube
Definition: A tube containing plasma which is created by a radiofrequency field.
Description: An RF generator is attached to the RF tube and is used to generate the plasma. The tube typically contains a gas or a mixture of gases. As the gas is ionized, free electrons are accelerated in the field and collide with the atoms thereby exciting the atoms. As the atoms are de-excited photons are emitted resulting in visible or ultraviolet emission. A picture of an RF plasma tube is shown in Figure 6. Common frequencies are 13.56 MHz and 2.45 GHz.
Figure 6: A radiofrequency plasma tube
[Source: Gas Plasma Tube For High Power RF (plasmasonics.com)]
6. Microwave or Radiofrequency (RF) diathermy equipment
Definition: Microwave diathermy equipment uses electromagnetic energy in the microwave frequency range (300 MHz to 300 GHz) for therapeutic purposes.
Whilst, RF diathermy equipment uses electromagnetic energy in the frequency range (3-30 MHz) for therapeutic purposes.
In Australia the only approved frequency for microwave diathermy treatment is 2450 MHz.
RF diathermy is sometimes referred to as shortwave diathermy. In Australia the only approved frequency for RF diathermy is 27.12 MHz. A picture of a diathermy unit is shown in Figure 7.
Figure 7: Diathermy unit
[Source: China Microwave Diathermy, Microwave Diathermy Wholesale, Manufacturers, Price | Made-in-China.com]
Note: Microwave and RF diathermy are not used very much nowadays and very few licence holders have this apparatus. In both microwave diathermy and RF diathermy heating of muscular tissue is performed for therapeutic reasons. In surgical diathermy a high-frequency electric current is made to pass through the body between two contact electrodes. The frequency is lower than for RF diathermy, typically 0.5–3 MHz. Surgical diathermy is not included in the above definition for microwave and radiofrequency diathermy equipment.
7. Industrial microwave processing system
Definition: A system where energy in the form of microwaves is used for heating or drying. Industrial signifies that the apparatus is not used for domestic applications.
Common microwave frequencies are 915 MHz, 2.45 GHz and 5.8 GHz. An industrial microwave is considered an industrial microwave processing system.
Figure 8: Industrial microwave processing system
[Source: Continuous Microwave Ovens | Cellencor]
8. Industrial radiofrequency processing system
Definition: A system where energy in the form of radiofrequency waves is used for heating or drying. Industrial signifies that the apparatus is not used for domestic applications.
The most common RF frequencies are 13.56 MHz, 27.12 MHz and 40.68 MHz. Note that the definition for an industrial RF processing system is similar to the definition for an industrial RF heater. Typically an industrial RF processing system is a large enclosed unit used for large scale heating or drying (see Figure 9).
Radiofrequency and microwave processing systems are frequently used for heating and drying of materials such as paper, ceramics, food and plastics. Heating through RF and microwave is fast compared with conventional heating mechanisms which makes them a preferred option for pasteurization and sterilization. Microwave heating is a common choice in a laboratory environment. The heating mechanism is the same in RF heating, the only difference being the lower frequency. The selection of RF or microwave heating depends on the physical properties of the process. The penetration depth is greater for RF (longer wavelength) which can therefore be more suited for larger scale systems. RF systems also have a greater uniformity of heating.
Figure 9: Industrial RF processing system used for drying products
[Source: General Industry - Radio Frequency Co. - Industrial]
Appendix 2: Extracts from RPS S-1 Limiting Exposure to RF Fields – 100 kHz to 300 GHz (2021)
General information
The standard includes:
- mandatory basic restrictions for both occupational and general public exposure involving the whole body and also for exposure over localised areas of the body
- indicative reference levels for measurable quantities derived from the basic restrictions
- approaches for verification of compliance with the standard
- requirements for management of risk in occupational exposure and measures for protection of the general public
Basic Restrictions:
Mandatory limits on exposure to RF fields are based on established health effects and are termed ‘basic restrictions’. Depending on the frequency the physical quantities used to specify the basic restrictions are induced electric field (Eind), specific absorption rate (SAR), specific energy absorption (SA) and absorbed energy density (Uab). These quantities are often impractical to measure. Therefore reference levels are measured as an alternative means of showing compliance with the mandatory basic restrictions.
Reference Levels:
Reference levels using quantities that are more practical to measure have been developed. The reference levels have been conservatively formulated such that compliance with the reference levels will ensure compliance with the basic restrictions. Provided that all basic restrictions are met and adverse effects can be excluded, the reference levels may be exceeded. Hence the reference levels have been conservatively formulated such that compliance with the reference levels will ensure compliance with the basic restrictions. The relevant reference level quantities are incident electric field strength (Einc), incident magnetic field strength (Hinc), incident power density (Sinc), plane-wave equivalent incident power density (Seq), incident energy density (Uinc), and plane-wave equivalent incident energy density (Ueq), all measured outside the body, and electric current (I) inside the body.
Reference levels are given for occupational exposure and exposure to the general public. These groups are distinguished by their potential level of exposure.
In the extract from RPS S-1 below, reference levels are specified in Tables 4 - 7 and have been set to protect against effects associated with:
- Table 4 whole body exposure (averaged over 30 minutes)
- Table 5 local exposure (averaged over 6 minutes)
- Table 6 brief local exposure (integrated over intervals between >0 and <6 minutes)
- Table 7 instantaneous local exposure (peak instantaneous field strength)
For further information see Radiation Protection Series S-1.
Table 4: Reference levels for whole body exposure averaged over 30 minutes to RF electromagnetic fields from 100 kHz to 300 GHz (unperturbed rms fields)
| Exposure Scenario | Frequency range | Incident E-field strength Einc (V/m) |
Incident H-field strength Hinc (A/m) |
Incident power density Sinc (W/m2) |
|---|---|---|---|---|
| Occupational | 0.1-6.943MHz | ES | 4.9/fM | NA |
| >6.943-30 MHz | 660/fM0.7 | 4.9/fM | NA | |
| >30-400 MHz | 61 | 0.16 | 10 | |
| 400–2000MHz | 3fM 0.5 | 0.008fM 0.5 | fM /40 | |
| 2–300 GHz | NA | NA | 50 | |
| General Public | 0.1-6.27MHz | ES | 2.2/fM | NA |
| 6.27-30 MHz | 300/fM 0.7 | 2.2/fM | NA | |
| >30-400 MHz | 27.7 | 0.073 | 2 | |
| >400-2000 MHz | 1.375fM 0.5 | 0.0037fM 0.5 | fM/200 | |
| >2–300 GHz | NA | NA | 10 |
Notes:
- ‘NA’ signifies ‘not applicable’ and does not need to be taken into account when determining compliance.
- ‘ES’ signifies that no reference level is available, as it would be greater than the reference level for spatial peak and temporal peak field strengths based on electrostimulation effects shown in Table 7.
- fM is frequency in MHz.
- Sinc, Einc and Hinc are to be averaged over 30 minutes, over the whole-body space. Temporal and spatial averaging of each of Einc and Hinc must be conducted by averaging over the relevant square values (see ICNIRP guidelines for limiting exposure to electromagnetic fields (100 kHz to 300 GHz), Health Physics, 118(5):483–524 for details) see International best practice - non-ionising radiation safety | ARPANSA.
- For frequencies of 100 kHz to 30 MHz, regardless of the far-field/near-field zone distinctions, compliance is demonstrated if neither Einc nor Hinc exceeds the above reference level values.
- For frequencies of >30 MHz to 2 GHz: a) within the far-field and radiating near field zones: compliance is demonstrated if either Sinc, Einc or Hinc, does not exceed the above reference level values (only one is required); Seq derived from either Einc or Hinc may be substituted for Sinc; b) within the reactive near-field zone: compliance is demonstrated if both Einc and Hinc do not exceed the above reference level values; Sinc cannot be used to demonstrate compliance, and so basic restrictions must be assessed.
- For frequencies of >2 GHz to 300 GHz: a) within the far-field and radiating near field zones: compliance is demonstrated if Sinc does not exceed the above reference level values; Seq derived from either Einc or Hinc may be substituted for Sinc; b) within the reactive near-field zone, reference levels cannot be used to determine compliance, and so basic restrictions must be assessed.
Table 5: Reference levels for local exposure averaged over 6 minutes, to electromagnetic fields from 100 kHz to 300 GHz (unperturbed rms fields)
| Exposure Scenario | Frequency range | Incident E-field strength Einc (V/m) |
Incident H-field strength Hinc (A/m) |
Incident power density Sinc (W/m2) |
|---|---|---|---|---|
| Occupational | 0.1-0.135 MHz | ES | ES | NA |
| >0.135-10 MHz | ES | 10.8/fM | NA | |
| >10-30 MHz | 1504/fM0.7 | 10.8/fM | NA | |
| >30-400 MHz | 139 | 0.36 | 50 | |
| >400-2000 MHz | 10.58fM0.43 | 0.0274fM0.43 | 0.29fM0.86 | |
| >2-6 GHz | NA | NA | 200 | |
| >6-<300 GHz | NA | NA | 275/fG0.177 | |
| 300 GHz | NA | NA | 100 | |
| General Public | 0.1-0.233 MHz | ES | ES | NA |
| >0.233-10 MHz | ES | 4.9/fM | NA | |
| >10-30 MHz | 671/fM 0.7 | 4.9/fM | NA | |
| >30-400 MHz | 62 | 0.163 | 10 | |
| >400-2000 MHz | 4.72fM 0.43 | 0.0123fM 0.43 | 0.058fM 0.86 | |
| >2-6 GHz | NA | NA | 40 | |
| >6-<300 GHz | NA | NA | 55/fG 0.177 | |
| 300 GHz | NA | NA | 20 |
Notes:
- ‘NA’ signifies ‘not applicable’ and does not need to be taken into account when determining compliance.
- ‘ES’ signifies that no reference level is available, as it would be greater than the reference level for spatial peak and temporal peak field strengths based on electrostimulation effects shown in Table 7.
- fM is frequency in MHz; fG is frequency in GHz.
- Sinc, Einc and Hinc are to be averaged over 6 minutes, and where spatial averaging is specified in Notes 6-7, over the relevant projected body space. Temporal and spatial averaging of each of Einc and Hinc must be conducted by averaging over the relevant square values (see ICNIRP guidelines for limiting exposure to electromagnetic fields (100 kHz to 300 GHz), Health Physics, 118(5):483–524 for details) see link International best practice - non-ionising radiation safety | ARPANSA to the ICNIRP website.
- For frequencies of 100 kHz to 30 MHz, regardless of the far-field/near-field zone distinctions, compliance is demonstrated if neither peak spatial Einc nor peak spatial Hinc, over the projected whole-body space, exceeds the above reference level values.
- For frequencies of >30 MHz to 6 GHz: a) within the far-field and radiating near field zones, compliance is demonstrated if one of peak spatial Sinc, Einc or Hinc, over the projected whole-body space, does not exceed the above reference level values (only one is required); Seq derived from either Einc or Hinc may be substituted for Sinc; b) within the reactive near-field zone: compliance is demonstrated if both Einc and Hinc do not exceed the above reference level values; Sinc cannot be used to demonstrate compliance; for frequencies >2 GHz, reference levels cannot be used to determine compliance, and so basic restrictions must be assessed.
- For frequencies of >6 GHz to 300 GHz: a) within the far-field and radiating near field zones, compliance is demonstrated if Sinc, averaged over a square 4 cm2 projected body surface space, does not exceed the above reference level values; Seq derived from either Einc or Hinc may be substituted for Sinc; b) within the reactive near-field zone, reference levels cannot be used to determine compliance, and so basic restrictions must be assessed.
- For frequencies of >30 GHz to 300 GHz, exposure averaged over a square 1-cm2 projected body surface space must not exceed twice that of the square 4 cm2 Sinc restrictions.
Table 6: Reference levels for local exposure, integrated over intervals of between >0 and <6 minutes to RF electromagnetic fields from 100 kHz to 300 GHz (unperturbed rms fields)
| Exposure Scenario | Frequency range | Incident energy density Uinc (kJ/m2) |
|---|---|---|
| Occupational | 100 kHz – 400 MHz | NA |
| >400 – 2000 MHz | 0.29fM0.86 x 0.36(0.05+0.95[t/360]0.5) | |
| >2 – 6 GHz | 200 x 0.36(0.05+0.95[t/360]0.5) | |
| >6 – <300 GHz | 275/fG0.177 x 0.36(0.05+0.95[t/360]0.5) | |
| 300 GHz | 100 x 0.36(0.05+0.95[t/360]0.5) | |
| General Public | 100 kHz – 400 MHz | NA |
| >400 – 2000 MHz | 0.058fM0.86 x 0.36(0.05+0.95[t/360]0.5) | |
| >2 – 6 GHz | 40 x 0.36(0.05+0.95[t/360]0.5) | |
| >6 – <300 GHz | 55/fG0.177 x 0.36(0.05+0.95[t/360]0.5) | |
| 300 GHz | 20 x 0.36(0.05+0.95[t/360]0.5) |
Notes:
- ‘NA’ signifies ‘not applicable’ and does not need to be taken into account when determining compliance.
- fM is frequency in MHz; fG is frequency in GHz; t is the exposure time interval in seconds, such that exposure from any pulse, group of pulses, or subgroup of pulses in a train, as well as from the summation of exposures (including non-pulsed RF electromagnetic fields), delivered in t seconds, must not exceed these reference level values for any time 0 < t < 360 s.
- Uinc is to be calculated over time t, and where spatial averaging is specified in Notes 5-7, over the relevant projected body space.
- For frequencies of 100 kHz to 400 MHz, >0 to <6-minute restrictions are not required and so reference levels have not been set.
- For frequencies of >400 MHz to 6 GHz: a) within the far-field and radiating near field zones: compliance is demonstrated if peak spatial Uinc, over the projected whole-body space, does not exceed the above reference level values; Ueq derived from either Einc or Hinc may be substituted for Uinc; b) within the reactive near-field zone, reference levels cannot be used to determine compliance, and so basic restrictions must be assessed.
- For frequencies of >6 GHz to 300 GHz: a) within the far-field or radiative near-field zone, compliance is demonstrated if Uinc, averaged over a square 4 cm2 projected body surface space, does not exceed the above reference level values; Ueq derived from either Einc or Hinc may be substituted for Uinc; b) within the reactive near-field zone, reference levels cannot be used to determine compliance, and so basic restrictions must be assessed.
- For frequencies of >30 GHz to 300 GHz: exposure averaged over a square 1cm2 projected body surface space must not exceed 275/fG0.177 x 0.72(0.025+0.975[t/360]0.5) kJ/m2 for occupational and 55/fG0.177 x 0.72(0.025+0.975[t/360]0.5) kJ/m2 for general public exposure.
Table 7: Reference levels for spatial peak and temporal peak field strength to RF electromagnetic fields from 100 kHz to 300 GHz (unperturbed rms fields)
| Exposure Scenario | Frequency range | Incident E-field strength Einc (V/m) |
Incident H-field strength Hinc (A/m) |
|---|---|---|---|
| Occupational | 100 kHz – 10 MHz | 170 | 80 |
| General Public | 100 kHz – 10 MHz | 83 | 21 |
Notes:
- Regardless of the far-field/near-field zone distinction, compliance is demonstrated if neither the temporal nor spatial peak Einc or Hinc, over the space occupied by the body, exceeds the above reference level values.
The figures for occupational and general public reference levels for whole body and local exposure to RF electromagnetic fields as specified in tables 4 and 5 can be found in RPS S-1 Schedule 1.
Reference levels for limb currents
Limb current reference levels have been set to account for effects of grounding near human body resonance frequencies that might otherwise lead to reference levels underestimating exposures within tissue at certain RF electromagnetic field frequencies (averaged over 6 minutes – see Table 8) Limb current reference levels are only relevant in exposure scenarios where a person is not electrically isolated from a ground plane.
Table 8: Reference levels for current induced in any limb averaged over 6 minutes at frequencies between 100 kHz and 110 MHz
| Exposure Scenario | Frequency range | Current I (mA) |
|---|---|---|
| Occupational | 10 MHz – 110 MHz | 100 |
| General Public | 10 MHz – 110 MHz | 45 |
Notes:
- Current intensity values must be determined by averaging over the relevant square values (see ICNIRP guidelines for limiting exposure to electromagnetic fields (100 kHz to 300 GHz), Health Physics, 118(5):483–524 for details), the document can be downloaded from the ARPANSA website link International best practice - non-ionising radiation safety | ARPANSA to the ICNIRP website.
- Limb current intensity must be evaluated separately for each limb.
- Limb current reference levels are not provided for any other frequency range.
- Limb current reference levels are only required for cases where the human body is not electrically isolated from a ground plane.
Tables 4 to 8 specify averaging and integrating times of the relevant exposure quantities to determine whether personal exposure level is compliant with the Standard. These averaging and integrating times are continuous periods.
Guidance for contact currents
Exposure due to contact currents is indirect, in that it requires an intermediate conducting object to transduce the field. This makes contact current exposure unpredictable, due to both behavioural factors (e.g., grasping versus touch contact) and environmental conditions (e.g., configuration of conductive objects), and reduces this Standard’s ability to protect against them. Accordingly, the ICNIRP guidelines and the Standard do not provide restrictions for contact currents, and instead provide ‘guidance’ to assist those responsible for transmitting high-power RF fields to understand contact currents, the potential hazards, and how to mitigate such hazards.
In determining the likelihood and nature of the hazard due to potential contact current scenarios, ICNIRP views the following as important for the Responsible Person in managing risk associated with contact currents within the 100 kHz to 110 MHz region.
(a) Contact current thresholds for reversible, mild pain, for adults and children, are likely to be approximately 20 mA and 10 mA respectively.
(b) Contact current magnitude will increase as a function of field strength and is affected by conducting-object configuration such as the proximity to the original source and the angular alignment to the original source.
(c) Risk of contact current hazards can be minimized by training workers to avoid contact with conducting objects, but where contact is required, the following factors are important:
i. Large conducting objects should be connected to ground (grounding).
ii. Workers should make contact via insulating materials or PPE (e.g., RF protective gloves).
iii. Reducing or removing the RF power at the original source can eliminate the risk.
iv. Workers should be made aware of the risks, including the possibility of ‘surprise’, which may impact on safety in ways other than the direct impact of the current on tissue (for example, by causing accidents when working at heights).
Appendix 3: Extracts from the ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields 1Hz-100 kHz (2010)
General information
This publication establishes guidelines for limiting exposure to electric and magnetic fields in the low frequency range of the electromagnetic spectrum. Separate guidance is given for occupational and general public exposures.
Reference Levels
A summary of the reference levels recommended for occupational and general public exposures to electric and a magnetic field is given in Tables 3 and 4.
Table 3: Reference levels for occupational exposure to time-varying electric and magnetic fields (unperturbed rms fields)
| Frequency range | E-field strength E (kV/m-1) |
Magnetic-field strength H (A m-1) |
Magnetic flux density B (T) |
|---|---|---|---|
| 1 Hz-8 Hz | 20 | 1.63x105/f2 | 0.2/f2 |
| 8 Hz-25 Hz | 20 | 2x104/f | 2.5x10-2/f |
| 25 Hz-300 Hz | 5x102/f | 8x102 | 1x10-3 |
| 300 Hz-3 kHz | 5x102/f | 2.4x105/f | 0.3/f |
| 3 kHz-10 MHz | 1.7x10-1 | 80 | 1x10-4 |
Notes:
- f in Hz
- Refer ICNIRP Guidelines separate sections for advice on non-sinusoidal and multiple frequency exposure
- To prevent indirect effects especially in high electric fields, see section on “Protective measures” in the ICNIRP Guidelines
- In the frequency range above 100 kHz, RF specific reference levels need to be considered additionally.
Table 4: Reference levels for general public exposure to time-varying electric and magnetic fields (unperturbed rms values)
| Frequency range | E-field strength E (kV/m-1) |
Magnetic-field strength H (A m-1) |
Magnetic flux density B (T) |
|---|---|---|---|
| 1 Hz-8 Hz | 5 | 3.2x104/f2 | 4x10-2/f2 |
| 8 Hz-25 Hz | 5 | 4x103/f | 5x10-3/f |
| 25 Hz-50 Hz | 5 | 1.6x102 | 2x10-4 |
| 50 Hz-400 Hz | 2.5x102/f | 1.6x102 | 2x10-4 |
| 400 Hz-3 kHz | 2.5x102/f | 6.4x104/f | 8x10-2/f |
| 3 kHz-10 MHz | 8.3x10-2 | 21 | 2.7x10-5 |
Notes:
- f in Hz
- Refer ICNIRP Guidelines separate sections for advice on non-sinusoidal and multiple frequency exposure
- In the frequency range above 100 kHz, RF specific reference levels need to be considered additionally
For further information on the ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields 1Hz-100 kHz see International best practice - non-ionising radiation safety | ARPANSA.
