To exempt certain conductors from the requirements
of Sentence 18.104.22.168.(2), on the basis that:
- emergency lighting units within the same storey need
not operate for extended periods of time as it is assumed that occupants
will rapidly vacate the floor of fire origin, and
- it is assumed that a fire within the same storey will
render emergency lighting units inoperative as they are not tested
nor designed to operate continually under fire conditions.