I shudder to think what would have happened if my brother had not saved my life last month. I had returned from a trip to Germany and had fallen off to sleep leaving my geyser switched on. The geyser overheated, developed a short circuit .Smoke emanated from the bathroom but I lay nearly unconscious in my bed. My brother came into my room to take his digital camera and found the geyser smoking. Without further delay he installed a smoke detector. I found the Kidde Smoke Detector very helpful. Our wireless system also had AC powered unit and battery operated unit in- built in it. Whether it is smoke or flames, this device detects fast and all the interconnected alarms go off. These are inexpensive and durable too.