Smoke Alert Alarm System

9V battery missing. No mention of the battery in the website. That's not smart it's cheating not to mention battery is or not part of OE.

Totally useless product. It stopped working within 3 weeks by which time it was unreturnable. The alarm sounded every time a battery was connected. I followed the advice in the instructions to change the battery but this made no difference. Despite this being a clearly defective device which is meant to save lives, Amazon refused a refund, and said the seller would contact me within 2 days (there is no way of contacting the seller myself). I’ve heard nothing. A waste of money - steer clear and spend more on a trusted brand.

Best Among the four models from different vendors. Very loud sound even though it says 85 Decibels.