Does an Automatic Transfer Switch used in smoke control systems require a maintenance bypass?

Clause 9 of “BS8519 Selection and installation of fire-resistant power and control cable systems for life safety, fire-fighting and other critical applications. Code of practice” states that where the availability of the safety and firefighting equipment is conditional to the occupation of the building, which it is in the case of a smoke control system, a bypass arrangement should be incorporated to enable the changeover device to be maintained without loss of service from the critical plant. This enables the supply to the system to be available when the ATS is out of service due to maintenance.