Know The Facts: Residential Smoke Alarms

Published On
Mar 15, 2016

Each year, the National Fire Protection Association (NFPA) publishes fire statistics. Residential typically leads all other occupancy types in fires, injuries and deaths. However, since the advent of the residential smoke alarm, residential fire deaths have fallen by more than 50 percent. 


Anyone who provides smoke alarms in residential applications should understand the most recent NFPA 72, National Fire Alarm and Signaling Code, requirements. Occupancies where the residential building codes and fire codes typically require smoke alarms include residential, residential board and care, and daycare homes. 


According to the code’s definition, a “residential occupancy” provides sleeping accommodations for purposes other than healthcare or detention and correctional occupancies and includes one- and two-family dwellings; lodging or rooming houses; hotels, motels and dormitories; and apartment buildings. 


A “residential board and care occupancy” provides lodging and boarding for four or more residents not related by blood or marriage to the owners or operators. It provides personal care services and includes small (not more than 16 residents) and large facilities.


A “daycare home” is a specific category of daycare occupancy that includes a building or portion of a building in which more than three—but not more than 12—clients receive care, maintenance and supervision by other than their relatives or legal guardians for less than 24 hours per day.


In various jurisdictions, laws, codes or standards might include conditions that could affect the applicability of these requirements. Contractors should consult the local authority, both the building and fire inspectors, for specific details.


Chapter 29 contains requirements for the number and placement of smoke alarms. Specifically, the code requires the installation of single- and multiple-
station smoke alarms in the following areas:


• All sleeping rooms and guest rooms


• Outside of each separate dwelling unit sleeping area, within 21 feet of any door to a sleeping room, with the distance measured along a path of travel


• Every level of a dwelling unit, including basements (and where separated from the adjacent living areas by a door and sleeping rooms, one shall be on each side of the door)


• Every level of a residential board and care occupancy (small facility), including basements and excluding crawl spaces and unfinished attics


• The living area(s) of a guest suite


• The living area(s) of a residential board and care occupancy (small facility)


When a very large residence contains floor areas greater than 1,000 square feet (excluding garage areas), the code requires smoke alarms installed on the ceiling, and all points on the ceiling must have a smoke alarm within 30 feet or have an equivalent of one smoke alarm per 500 square feet of floor area. To determine the correct number of detectors, divide the total interior square footage of floor area per level by 500 square feet. 


Where dwelling units include great rooms or vaulted/cathedral ceilings extending the equivalent height of multiple floors, the code permits smoke alarms located on the upper floor that intend to protect these areas to meet the requirements, because the code considers these smoke alarms as part of the lower floors’ protection scheme. 


The code permits the installation of smoke alarms on the wall. In fact, building configurations, such as room divisions and open foyers or great rooms, dictate smoke-alarm locations so that they do not cover distinctly separate 500-square-foot areas. Instead, they provide overlapping coverage relative to the code-required spacing.


Since the NFPA 72 2007 development, the interconnection of smoke alarms for new and existing construction is required. The introduction of wirelessly interconnected smoke alarms provides an alternative method to interconnect devices in existing construction without the need for wiring modifications that once offered the only alternative. Battery replacement presents the obvious drawback to any wireless device. However, most units on the market contain 10-year batteries to help mitigate that issue.


Underwriters Laboratories (UL) has two smoke alarm categories which presents another relatively unknown factor. The first listing category (UTGT) provides for smoke-alarm applications where sensitivity testing is not required. The second (UTHA) provides for smoke-alarm applications where such testing is required. Alarms in the latter category would follow Chapter 14’s testing requirements.


The environment must be considered for smoke-alarm placement in residential occupancies. Smoke-alarm placement in attics, garages and in or too close to a kitchen cause far too many false or nuisance alarms. The code does not permit installation in these areas.

About the Author

Wayne D. Moore

Fire/Life Safety Columnist

Wayne D. Moore, a licensed fire protection engineer, frequent speaker, writer and expert in the life safety field, has been a principal member and chair of NFPA 72, Chapter 24, as well as a former principal member of NFPA 909 and NFPA 914. He is the...

Stay Informed Join our Newsletter

Having trouble finding time to sit down with the latest issue of
ELECTRICAL CONTRACTOR? Don't worry, we'll come to you.