Bit of a grey area. Heres my opinion for what its worth.
First of all to add to the confusion we have two situations. Green break glass boxes are most commonly provided to over ride a magnetic door lock on conventional hinged doors, and can also be used to over ride powered sliding doors. In this case, because the green box usually breaks both poles of a circuit, the powered sliding doors are already configured to fail safe of power failure.
If the doors are operated by PIR sensor AND have fail safe operation (power fails doors open) / battery backup a green box is not a requirement, as long as the doors will always be in automatic mode. (usually controlled by key switch). The weakness of this arrangement is that if the PIR fails we lose the exit and PIRs are rarely to a life safety standard. But I believe this arrangement is considered acceptable together with management procedures to ensure they remain in auto mode..
If the doors are linked to the fire alarm and fail safe in open position on power failure/ battery backup AND they have a standard push rocker switch to allow them to be opened for general use or other types of emergency they do not need a green break glass . The weakness of this arrangement is that in the event of an earth fault the rocker switch may only switch one pole and so the lock could fail to release ( if the earth fault and fire occur at the same time)
If the doors are PIR operated AND linked to the fire alarm no green box required.
If the doors hinge outwards if pushed (some sliding ones do) no green box needed.
If sliding doors have security controls / swipe cards etc ( not suitable for public use) the must always be a green box fitted.
If the doors are not linked to the fire alarm system then a green box is also required
I bet I have missed a load out of this, but hope it helps
