The daft thing being if there was no main supply to the detectors it would be fully compliant as battery only is fully compliant in a rental , be it a minimum requirement.

Although in that case the smoke detectors would be immune to damaging surges on the mains - as there would be no path to conduct the surge to the detector.

   - Andy.

Agreed.  I don't know how we have managed all these years. 

Agreed.  I don't know how we have managed all these years. 

Like smoke detectors have been blowing off the ceilings with all those transients.

Load of nonsense SPD,s

Yet we're forced to install them. A recent NICEIC shock and awe essay in the recent publication shows no scientific reason for employing spds just a narrative from manufacturers with vested interests.

I think that engineering has departed the IET