89520. The Abus RWM90 is an optical smoke alarm that warns you when smoke develops, with a loud 85 decibel alarm. It is recommended for bedrooms, living rooms, children's rooms and corridors up to 40 square metres in size and is tested according to DIN EN 14604.. Loud 85 dB alarm. Room detection range: up to 40 square metres. Replaceable 3 volt lithium battery (CR123A) included. Hush function for 9 minutes