Replacing Transfer Switch - need to separate emergency?

[olc]

Basically replacing an existing standby power source and transfer switch. The transfer switch feeds an elevator, a panelboard (call it PP-1), and a couple smaller panelboards.
This is an apartment building (seniors).
I presume the elevator is not an emergency load.
PP-1 feeds emergency exit lighting (some of the corridor lighting and the stair light fixtures), some receptacles (intended for oxygen machines), and maybe a couple other misc. loads added over the years. The other panelboards have misc. loads added over the years (nothing legally required to have stand by).
We are installing a generator and new transfer switch.
The question is -how far are we obligated to separate out the emergency loads (lighting) from the other loads (to put on a separate transfer switch)?

 

[m sleem]

700.12 says max 10 sec.

 

[RB1]

OLC,

The elevator is usually considered to be a standby load, but it is permitted to be supplied by the emergency system per 620.91. The other loads could be a problem. The AHJ could consider this a repair and thus the existing conditions may be viewed as "existing nonconforming". I wouldn't count on it! Do the exit signs and egress illumination have battery back up?