[Al Skierkiewicz]

Originally Posted by M. Krass

Thanks, everyone.

A coworker that's more experienced working with architects told me it's a light source and the subscript represents the circuit it's on, but it's on a drawing that has no other light sources and it's a non-standard symbol, so I'm skeptical that's the case.

Also, several of them appear in the middle of structures that stretch from floor to ceiling, so it'd be peculiar to put in a light where nobody will see it.

The search continues...

It may be a safety light. One that remains on when all other lighting is turned off. It also may be a power failure lighting device. Since it is an archetectural drawing there should be other schedules attached in the drawing bundle. Find the one (or several) that list electrical details and look for the symbol in that list. There should be a reference to the fixture type and there may even be a bill of materials.