You're not getting replies because setting an egress path is a very trick thing. It is usually handled by an FPE (Fire Protection Engineer) and they are usually very good at what they do.
The rules are in the BOCA code, and the IBC, but they pretty much reference NFPA 101. Exit lights - head 'em toward the danged exit usually within 75', but LOTSA variables on that.
Emergency egress path must be lit to a minimum of 1 fc at the FLOOR level. You can handle this with batteries, UPS system, or even a genset.
If you use a genset in place of batteries, it must have a 90 minute fuel supply ON SITE, (Natural gas can not normally fulfill this requirement and requires approval of the AHJ) AND be ON LINE within 10 seconds of power failure, that is from 700-12, but you will also find it in NFPA 101, and 110.
Asking a generic question like that leaves way too many variables. Also, you're fire marshall must approve this path, they can probably help you out to establish this if you are going to take on the responsibility yourself.