Bill I know you wanted to have some more discussion about the benefits of putting the exit lights on a lighting circuit. Tony did a terrific job pointing out all the rules that tell you not to do it. But if I consider your scenario and it accidentally gets connected to a timed or switched circuit the exit lights would go onto battery when you switch out the lights and leave at night. Depending on the type of occupancy the lights could be required to stay on for as little as 30 minutes, that means dead batteries when you come in the morning and a potential for problems.
I think you are trying to compare the rational of connecting a smoke detector in a residence to lighting circuit. This works great in a house, if the lights are out you have no smoke detector protection and know something is wrong right away. In theory it might make sense with exit lights, but I think the fire code protects us from this sort thing by requiring the owner/operator/tenant of a facility to test these lights monthly
Emergency lighting
2.7.3.3.
(1) Pilot lights on emergency lighting unit equipment shall be checked monthly for operation.
(2) Emergency lighting unit equipment shall be inspected monthly to ensure that
(a) the terminal connections are clean, free of corrosion and lubricated when
necessary,
(b) the terminal clamps are clean and tight as per manufacturer's specifications,
(c) the electrolyte level and specific gravity are maintained as per manufacturer's
specifications, and
(d) the battery surface is kept clean and dry.
(3) Emergency lighting unit equipment shall be tested
(a) monthly to ensure that the emergency lights will function upon failure of the
primary power supply, and
(b) annually to ensure that the unit will provide emergency lighting for a duration
equal to the design criteria under simulated power failure conditions.
(4) After completion of the test required in Clause (3)(b), the charging conditions for voltage
and current and the recovery period shall be tested to ensure that the charging system is in
accordance with the manufacturer's specifications.
