Aico's EI161E Ionisation Smoke Alarm has a Lithium back-up battery with a 10 year life. Best for fast-flaming fires (Papers, Clothing) Proven long life ionisation smike chamber BS EN 14604:2005 KM 522831
“Bought as a replacement for an older smoke alarm. Very straightforward to install although no mention in instructions that battery wire from original alarm can’t be connected to new version. Original has 4 wires replacement 3.”