The regulation will not apply under conditions where
natural light will have an adverse effect on the process or material used in a room, or where the process in a room
has to be conducted under critical conditions of light, temperature, humidity or air movement, or where the
judgement of texture or colour in a room has to be done under conditions of constant lighting quality and intensity,
or where, for reasons of safety, privacy or security, compliance with the intended provisions becomes
impracticable.