Division B ACTION LEVELS (ALs)
United Kingdom
The following physical quantities and values are used to specify the action levels (ALs), the magnitude of which are established to ensure by simplified assessment the compliance with relevant ELVs or at which relevant protection or prevention measures specified in Article 5 must be taken:
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Low ALs(E) and high ALs(E) for electric field strength E of time varying electric fields as specified in Table B1;
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Low ALs(B) and high ALs(B) for magnetic flux density B of time varying magnetic fields as specified in Table B2;
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ALs(IC) for contact current as specified in Table B3;
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ALs(B0) for magnetic flux density of static magnetic fields as specified in Table B4.
ALs correspond to calculated or measured electric and magnetic field values at the workplace in the absence of the worker.
Action levels (ALs) for exposure to electric fields
Low ALs (Table B1) for external electric field are based on limiting the internal electric field below the ELVs (Tables A2 and A3) and limiting spark discharges in the working environment.
Below high ALs, the internal electric field does not exceed the ELVs (Tables A2 and A3) and annoying spark discharges are prevented, provided that the protection measures referred to in Article 5(6) are taken.
Table B1
ALs for exposure to electric fields from 1 Hz to 10 MHz
| Frequency range | Electric field strength Low ALs (E)[Vm–1] (RMS) | Electric field strength High ALs (E) [Vm–1] (RMS) |
|---|---|---|
| 1 ≤ f < 25 Hz | 2,0 × 104 | 2,0 × 104 |
| 25 ≤ f < 50 Hz | 5,0 × 105/f | 2,0 × 104 |
| 50 Hz ≤ f < 1,64 kHz | 5,0 × 105/f | 1,0 × 106/f |
| 1,64 ≤ f < 3 kHz | 5,0 × 105/f | 6,1 × 102 |
| 3 kHz ≤ f ≤ 10 MHz | 1,7 × 102 | 6,1 × 102 |
Action levels (ALs) for exposure to magnetic fields
Low ALs (Table B2) are, for frequencies below 400 Hz, derived from the sensory effects ELVs (Table A3) and, for frequencies above 400 Hz, from the health effects ELVs for internal electric field (Table A2).
High ALs (Table B2) are derived from the health effects ELVs for internal electric field related to electric stimulation of peripheral and autonomous nerve tissues in head and trunk (Table A2). Compliance with the high ALs ensures that health effects ELVs are not exceeded, but the effects related to retinal phosphenes and minor transient changes in brain activity are possible, if the exposure of the head exceeds the low ALs for exposures up to 400 Hz. In such a case, Article 5(6) applies.
ALs for exposure of limbs are derived from the health effects ELVs for internal electric field related to electric stimulation of the tissues in limbs by taking into account that the magnetic field is coupled more weakly to the limbs than to the whole body.
Table B2
ALs for exposure to magnetic fields from 1 Hz to 10 MHz
| Frequency range | Magnetic flux density Low ALs(B)[μT] (RMS) | Magnetic flux density High ALs(B) [μT] (RMS) | Magnetic flux density ALs for exposure of limbs to a localised magnetic field [μT] (RMS) |
|---|---|---|---|
| 1 ≤ f < 8 Hz | 2,0 × 105/f2 | 3,0 × 105/f | 9,0 × 105/f |
| 8 ≤ f < 25 Hz | 2,5 × 104/f | 3,0 × 105/f | 9,0 × 105/f |
| 25 ≤ f < 300 Hz | 1,0 × 103 | 3,0 × 105/f | 9,0 × 105/f |
| 300 Hz ≤ f < 3 kHz | 3,0 × 105/f | 3,0 × 105/f | 9,0 × 105/f |
| 3 kHz ≤ f ≤ 10 MHz | 1,0 × 102 | 1,0 × 102 | 3,0 × 102 |
Table B3
ALs for contact current IC
| Frequency | ALs (IC) steady state contact current [mA] (RMS) |
|---|---|
| up to 2,5 kHz | 1,0 |
| 2,5 ≤ f < 100 kHz | 0,4 f |
| 100 ≤ f ≤ 10 000 kHz | 40 |
Action levels (ALs) for magnetic flux density of static magnetic fields
Table B4
ALs for magnetic flux density of static magnetic fields
| Hazards | ALs(B0) |
|---|---|
| Interference with active implanted devices, e.g. cardiac pacemakers | 0,5 mT |
| Attraction and projectile risk in the fringe field of high field strength sources (> 100 mT) | 3 mT |