A sleeping person may not wake up or collapse when they awaken. A fire can produce intense heat, which can exceed 1000 degrees. Breathing smoke and superheated air can cause lung damage. The body cannot regulate this amount of heat and can cause unconsciousness in minutes. To survive a home fire, you need to react immediately when one starts, and do some preplanning before one starts.
Smoke detectors save lives.
One should be installed in each sleeping room, and on every level, including the basement. Smoke detectors are not recommended for kitchens, bathrooms, attics, or garages. These areas are prone for nuisance alarms. In these areas you can install heat detectors to increase your protection. In other areas do not substitute heat detectors for smoke detectors.