Protecting Workers from Ultraviolet Radiation - icnirp

8.4.5 Moving Source
Protecting Workers from Ultraviolet Radiation
Sometimes the UV source is moving or the radiation field is changing its direction, e.g. a moving
UV spotlight beam. It may be difficult to determine an accurate cumulative exposure of people in
such cases.
8.4.6 Non-visible source radiation and reflections
It is rare that a UVR source does not also emit at least some visible radiation and the source itself
can be seen. However, one should not judge the source of radiation solely by what is visible.
For example, the character of reflections within the workplace can frequently not be judged from
the material characteristics in the visible spectrum. Many materials, such as most white paints are
not reflective in the UV spectral region, particularly in the UVB and UVC regions. Some
metals, particularly aluminium, maybe highly reflective in the ultraviolet wavelength range. For
instance, reflections might become relevant if protective measures, such as face shields, do not
protect against radiation from all directions.
8.4.7 Choice of instrumentation
In some situations where high accuracy is needed, a double-grating monochromater
spectroradiometer should be used to measure the spectral irradiance at a given reference point. A
broad-band radiometer would be used to determine the time or position dependent irradiance,
relative to the reference point measurement.
8.5 Relevant properties of measurement systems
For the measurement of exposure levels to be compared to the exposure limits as noted in
Paragraph 8.3.1, geometrical aspects of the exposure must be considered. The following
properties of measurement systems are relevant for obtaining valid data to be compared to
exposure limits. It is noted that the aperture diameter, field of view (FOV) (acceptance angle),
and the cosine dependence of the detector are important.
8.5.1 Irradiance averaging
The diameter of the input aperture of the detector does not have an impact on the measurement if
the irradiance profile is homogeneous. If there are hotspots in the irradiance profile, the diameter
of the aperture should be small enough to resolve the hotspot, however, it is usually not
necessary to use aperture diameters less than ~ 7 – 10 mm unless laser beams are being
measured.
8.5.2 Field of view (acceptance angle)
The field of view of the detector (the “part” of the world which is seen by the detector) should be
180° for measurements to be used for skin hazard assessment and should be limited to 80° (± 40
° from the normal) for measurements to be used for eye hazard assessment. The field of view for
eye evaluations does not play a role if the source is smaller than the field of view of the detector.
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