HM Government (Fire Safety Risk Assessment Guide for Residential Care Premises – ISBN-13:978 1 85112 818 1).

Page 126 states as follows:

“In all cases the automatic device should release the fire-resisting door allowing it to close effectively within its frame when any of the following conditions occur:

   the detection of smoke by an automatic detector;
   the actuation of the fire detection and alarm system by manual means e.g. operation of break glass call point;
   any failure of the fire detection and alarm system;
or
   any electrical power failure

Office of the Deputy Prime Minister – The Building Regulations 2000 – Approved Document M

Page 34 states as follows:

Internal doors will satisfy Requirement M1 or M2 if:

   Fire doors, particularly those in corridors, are held open with an electro-magnetic device, but self-close when activated by smoke detectors linked to the door individually, or to a main fire/smoke alarm system;
   The power supply fails;
   Activated by a hand-operated switch;
   Fire doors, particularly to individual rooms, are fitted with swing-free devices that close when activated by smoke detectors or the building’s fire alarm system, or when the power supply fails.

‍