BS EN 50496:2018 pdf download.Determination of workers’ exposure to electromagnetic fields and assessment of risk at a broadcast site
6.3 Additional considerations
6.3.1 Use of action levels
Compliance with the action levels will ensure compliance with the relevant exposure limit values. If the measured or calculated value exceeds the action levels, it does not necessarily follow that the exposure limit values will be exceeded.
6.3.2 Multiple exposure
With regard to simultaneous exposure to multiple frequency fields, it is important to identify multiple sources of exposure or simultaneous exposure to multiple frequency fields and to use appropriate methods of assessment, measurement and/or calculation capable of analysing the characteristics of the waveforms and nature of biological interactions (see flowcharts in Figures 1 to 3 and Annex A). Once identified, the combination of different frequency components should be carried out separately for thermal effects and electrical stimulation. The formulae in Annex A apply to the relevant frequencies under practical exposure situations and shall be used to establish compliance to the action levels or exposure limit values for all the frequencies together.
6.3.3 Polarization
To take in account the polarization and the incidence of signals, the field should be evaluated isotropically. If probes with a single sensor element responding only to one field component are used, they should be oriented to read the maximum value, or should be aligned in three mutually orthogonal directions to measure separately the spatial components of the field.
If spatial averaging is carried out, then a minimum of 3 measurement points shall be used (one point of these points shall be a maximum). However, where a source is localized within a distance of a few centimetres from the body, simple averaging may not be adequate to ensure compliance with local exposure limit values and so additional dosimetry is needed.
6.3.4.3 Time equivalent averaging
Spatial averaging in a typical situation such as an FMTV mast, where a worker is moving in an EMF produced by a constant intensity source, can be considered to be equivalent to time averaging on a stationary worker from a source whose intensity varies with time. The length of the averaging path is given by the product of the averaging time, (6 min), and the velocity of movement of the worker along that path. An assessment of the appropriate speed needs to be made, considering the type of mast.
BS EN 50496:2018 pdf download
