The following text refers to IEC 60335-2-27 Ed 5.0. Household and similar electrical appliances - Safety - Part 2-27: Particular requirements for appliances for skin exposure to ultraviolet and infrared radiation. One should ensure that this version is current at the time of reading and verify whether or not national deviations exist.
Clause 7.1 states that if an appliance has UV emitter with a luminance exceeding 100 000 cd.m-2, the appliance shall be marked with the substance of the following:-
WARNING: Intense light. Do not stare at the emitter.
Annex AA gives brief guidance on this measurement of the appliance, operated at the rated voltage. The measurement should be performed at the shortest distance possible from the light source, not less than 0.2m, with a solid angle of acceptance corresponding to a plane angle of 1°.
The luminance of 100 000 cd.m-2 is taken as one that is visually comfortable to view. Increasing luminance can give rise to glare.
The measurement of luminance can be performed in one of two ways.
1. Using a spectroradiometer with a telescope input optic, to perform measurements of spectral radiance over the spectral range 380-780nm. The resulting spectral radiance is weighted against the CIE V() function and scaled using 683 lumens/ Watt to obtain the luminance of the source in cd.m-2. The field of view of the telescope should measure an area smaller than the luminous area of the source.
2. Using a luminance meter to measure directly the luminance of the source. The field of view of the luminance meter should measure an area smaller than the luminous area of the source.