From the National Fire Alarm Code (NFPA 72), section A.11.8.3, in reference to adding smoke
detectors beyond what the code requires......
.......Are More Smoke Detectors Desirable? The required number of smoke detectors might
not provide reliable early warning protection for those areas separated by a door from the
areas protected by the required smoke detectors. For this reason, it is recommended that the
householder consider the use of additional smoke detectors for those areas for increased
protection. The additional areas include the basement, bedrooms, dining room, furnace room,
utility room, and hallways not protected by the required smoke detectors. The installation
of smoke detectors in kitchens, attics (finished or unfinished), or garages is not normally
recommended, as these locations occasionally experience conditions that can result in improper
operation.