Investigations into home fire deaths very often find that a smoke alarm did not sound. It may have been disconnected or not in working order. The batteries may have been dead, or someone may have taken them out.
Many fatal fires start at night. Smoke alone won't necessarily wake you up. In fact, the fumes could put you into an even deeper sleep. Often, victims never wake up. Only a working smoke alarm can save your life.
Make it a priority to test your alarms on a monthly basis and make sure you have a working detector on each level of your home.