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3. Exposure Limits

Disclaimer: This resource has been prepared to help the workplace parties understand some of their obligations under the Occupational Health and Safety Act (OHSA) and regulations. It is not legal advice. It is not intended to replace the OHSA or the regulations. For further information please see full disclaimer.

The recommended occupational exposure limits and measurement protocol set out in this guideline are extracted from the Health Canada guideline “Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kHz to 300 GHz – Safety Code 6 (2015)” commonly known as Safety Code 6. Workplaces which have the potential of approaching or exceeding these limits are encouraged to become familiar with this document and its technical guide.

Exposure limits for RF/MW radiation are designed to keep the RF/MW energy absorbed by the body well below the lowest levels associated with demonstrated adverse effects, and to reduce the likelihood of contact shocks and burns.

Since the RF/MW energy absorbed by the body varies with the frequency of the fields and since the rate of energy absorption is difficult to measure directly, the exposure limits are expressed in terms of frequency-dependent, root-mean-square (RMS) electric and magnetic field strengths, or in power density units (W/m2). Power density measures the amount of radiating energy crossing a given area in a given period of time.

Two recommended RF/MW exposure limits may apply in a workplace. Occupational exposure limits have been recommended for:

  • Uncontrolled spaces, which are areas in the workplace of unrestricted occupancy by workers.
  • Controlled spaces, which are only occupied by workers who have received RF/MW safety training. This training should include information about the RF/MW fields likely to be encountered, the potential health risks, and how these risks can be mitigated.

Protective measures such as, but not limited to, barriers, monitoring, administrative controls and personal protective devices, may need to be implemented to reduce the potential for worker exposure in excess of the recommended limits for both controlled and uncontrolled spaces.

Table I: Summary of Recommended Occupational Exposure Limits for Electric Field Strength, Magnetic Field Strength and Power Density in Uncontrolled Spaces
Frequency (MHz) Electric Field Strength; RMS (V/m) Magnetic Field Strength; RMS (A/m) Power Density (W/m2)[1] Averaging Time (minutes)
0.003 - 10 83 90 n/a Instantaneous
1.0 - 10 87/f 0.5 n/a n/a 6
0.1 - 10 n/a 0.73/f n/a 6
10 - 20 27.46 0.0728 2 6
20 - 48 58.07/f 0.25 0.1540/f 0.25 8.944/f 0.5 6
48 - 300 22.06 0.05852 1.291 6
300 - 6000 3.142f 0.3417 0.008335f 0.3417 0.02619f 0.6834 6
6000 - 15000 61.4 0.163 10 6
15000 - 150000 61.4 0.163 10 616000/f 1.2
150000 - 300000 0.158 f 0.5 4.21 x 10 -4 f 0.5 6.67 x 10 -5 f 616000/f 1.2

[1] Power density limit is applicable at frequencies greater than 10 MHz.

Notes:

The limits in Table I are based on Health Canada’s "Safety Code 6 (2015)".

  1. Frequency, f, is in MHz.
  2. A power density of 10 W/m2 is equivalent to 1 mW/cm2.
  3. A magnetic field strength of 1 A/m corresponds to 1.257 microtesla (μT) or 12.57 milligauss (mG).
  4. Values averaged over the worker’s head and torso.
  5. Both the electric and magnetic field strengths should be measured where no power density is shown.
  6. Notes found in Safety Code 6 should be referenced for a comprehensive interpretation of this table.
Table II: Summary of Recommended Occupational Exposure Limits for Electric Field Strength, Magnetic Field Strength and Power Density in Controlled Spaces
Frequency (MHz) Electric Field Strength; RMS (V/m) Magnetic Field Strength; RMS (A/m) Power Density (W/m2) [2] Averaging Time (minutes)
0.003 - 10 170 180 n/a Instantaneous
1.0 - 10 193/f 0.5 n/a n/a 6
0.1 - 10 n/a 1.6/f n/a 6
10 - 20 61.4 0.163 10 6
20 - 48 129.8/f 0.25 0.3444/f 0.25 44.72/f 0.5 6
48 - 100 49.33 0.1309 6.455 6
100 -6000 15.60f 0.25 0.04138f 0.25 0.6455f 0.5 6
6000 - 15000 137 0.364 50 6
15000 - 150000 137 0.364 50 616000/f 1.2
150000 - 300000 0.354 f 0.5 9.40 x 10 -4 f 0.5 3.33 x 10 -4 f 616000/f 1.2

[2] Power density limit is applicable at frequencies greater than 10 MHz.

Notes:

The limits in Table II are based on Health Canada’s "Safety Code 6 (2015)".

  1. Frequency, f, is in MHz.
  2. A power density of 10 W/m2 is equivalent to 1 mW/cm2.
  3. A magnetic field strength of 1 A/m corresponds to 1.257 microtesla (μT) or 12.57 milligauss (mG).
  4. Values averaged over the worker’s head and torso.
  5. Both the electric and magnetic field strengths should be measured where no Power Density is shown.
  6. Notes found in Safety Code 6 should be referenced for a comprehensive interpretation of this table.

In addition, workers should not be subject to RF contact shocks or burns. This can be achieved by reducing stray fields and installing appropriate insulation and grounding, or by ensuring that the electric current flowing between a worker and an object energized by electromagnetic fields does not exceed the values in Table III.

Table III: Recommended Induced and Contact Current Limits for Workers in Uncontrolled and Controlled Spaces
Frequency (MHz) Current Uncontrolled Spaces (mA, RMS) Controlled Spaces (mA, RMS) Averaging Time (minutes)
0.003 – 0.1 Contact 200 f 400 f Instantaneous
0.003 – 0.4 Induced 100 f 225 f Instantaneous
0.1 – 10 Contact 20 40 Instantaneous
0.4 - 110 Induced 40 90 6
10 - 110 Contact 20 40 6

Notes:

The limits in Table III are based on Health Canada’s "Safety Code 6 (2015)".

  1. Frequency, f, is in MHz.
  2. Current is in units of mA, RMS (milliampere root mean squared).
  3. Both Induced and Contact limits should be met.
  4. Notes found in Safety Code 6 should be referenced for a comprehensive interpretation of this table.

Table IV shows which sources of RF/MW radiation may expose workers to levels in excess of the recommended exposure limits for uncontrolled spaces.

Measurements of RF/MW levels should be carried out around sources with the potential to cause overexposure, in order to protect workers from overexposure to RF/MW radiation. Measurements are not necessary for sources which do not have the potential to produce exposures in excess of the occupational exposure limits for uncontrolled spaces. Special cases apply: an example is where a worker may be exposed to higher levels of RF/MW radiation when safety features are disabled during service or repairs.

Table IV: Sources of RF/MW Radiation
Source Frequency (MHz) Potential for over-exposure?
Video Display Terminal (CRT) 0.015 - 0.3 No
Dielectric Heater 1 - 100 (typically 27.12) Yes
Diathermy Applicator 13.56, 27.12, 915, 2450 Yes
Communications Transmitters: AM Radio 0.535 - 1.605 Yes
Communications Transmitters: FM Radio 88 - 108 Yes
Communications Transmitters: UHF VHF TV 54-72, 76-88, 174-216 Yes
Communications Transmitters: UHF Radio 470 - 890 Yes
Communications Transmitters: Dish Antenna 800 - 15000 Yes
CB Radio 27.12 Yes
Cordless Telephone 46 – 5800 No
Cellular Telephone 824 – 850, 900, 1800, 1900 No
Bluetooth Enabled Devices 2400 – 2480 No
Wi-Fi Router 2400 and 5000 No
Smart Electrical Meter 460, 902-928, 2400-2480, 1900 No
Security Scanner (mm Wave) 24000 and 30000 No
Traffic Radar 10500 and 24000 No
Microwave Oven 915 and 2450 No [3]

[3] Microwave ovens are constructed to meet stringent microwave leakage limits and to have safety interlocks, pursuant to federal legislation. When these interlocks are defeated, for example, during repair work, there is a risk of overexposure to microwave radiation.

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Disclaimer: This web resource has been prepared to assist the workplace parties in understanding some of their obligations under the Occupational Health and Safety Act (OHSA) and the regulations. It is not intended to replace the OHSA or the regulations and reference should always be made to the official version of the legislation.

It is the responsibility of the workplace parties to ensure compliance with the legislation. This web resource does not constitute legal advice. If you require assistance with respect to the interpretation of the legislation and its potential application in specific circumstances, please contact your legal counsel.

While this web resource will also be available to Ministry of Labour inspectors, they will apply and enforce the OHSA and its regulations based on the facts as they may find them in the workplace. This web resource does not affect their enforcement discretion in any way.