Anybody else ever had all the fire alarms in their house go off at once and had ALL the children sleep right through them, while you are running around dying from the sound, trying to figure out what the heck is going on?
That's not so surprising . . . there have been some studies on how some children will not wake up to the sound of many smoke detectors. It appears however that smoke detectors with an alternating pitch will have better results . . . and talking smoke detectors (some you can tape your own warning) have even better results at waking sleeping children.