The source and entrance equipment are typically in a separate room, but panels downstream from transfer switches don’t need to be.
NFPA 110 (similar for NFPA 111)
7.2.3* Level 1 EPSS equipment shall not be installed in the same room with the normal service equipment, where the service equipment is rated over 150 volts to ground and equal to or greater than 1000 amperes.
NEC 700
(D) Fire Protection. Emergency systems shall meet the additional requirements in (D)(1) through (D)(3) in the following occupancies:
(1) Assembly occupancies for not less than 1000 persons
(2) Buildings above 23 m (75 ft) in height
(3) Health care occupancies where persons are not capable of self preservation
(4) Educational occupancies with more than 300 occupants
(1) Feeder-Circuit Wiring. Feeder-circuit wiring shall meet one of the following conditions:
(1) The cable or raceway is installed in spaces or areas that are fully protected by an approved automatic fire suppression system.
(2) The cable or raceway is protected by a listed electrical circuit protective system with a minimum 2-hour fire rating.
Informational Note No. 1: Electrical circuit protective systems could include but not be limited to thermal barriers or a protective shaft and are tested to UL 1724, Fire Tests for Electrical Circuit Protection Systems.
Informational Note No. 2: The listing organization provides information for electrical circuit protective systems on proper installation requirements to maintain the fire rating.
(3) The cable or raceway is a listed fire-resistive cable system.
Informational Note No. 1: Fire-resistive cables are tested to ANSI/UL 2196, Tests for Fire Resistive Cables.
Informational Note No. 2: The listing organization provides information for fire-resistive cable systems on proper installation requirements to maintain the fire rating.
(4) The cable or raceway is protected by a listed fire-rated assembly that has a minimum fire rating of 2 hours and contains only emergency circuits.
(5) The cable or raceway is encased in a minimum of 50 mm (2 in.) of concrete.
(2) Feeder-Circuit Equipment. Equipment for feeder circuits (including transfer switches, transformers, and panelboards) shall be located either in spaces fully protected by approved automatic fire suppression systems (including sprinklers, carbon dioxide systems) or in spaces with a 2-hour fire resistance rating.
(3) Generator Control Wiring. Control conductors installed between the transfer equipment and the emergency generator shall be kept entirely independent of all other wiring and shall meet the conditions of 700.10(D)(1). The integrity of the generator control wiring shall be continuously monitored. Loss of integrity of the remote start circuit(s) shall initiate visual and audible annunciation of generator malfunction at the generator local and remote annunciator(s) and start the generator(s).
