Where to Place Smoke Detectors

4/24/2024

NFPA 72, National Fire Alarm and Signaling Code, is the model fire alarm systems installation standard that is incorporated into almost all building, fire, and local codes. However, there can often be confusion when adhering to the standard.  

Here are some more answers to commonly asked questions regarding NFPA 72: 

What functions does NFPA 72 require my fire alarm system to perform?  

The answer will depend on what type of fire alarm system is required by the building or life safety code that is in force in your jurisdiction and your corporate fire protection goals. Most fire alarm systems will have a manual fire alarm component in addition to monitoring the building’s automatic sprinkler system.  

A manual fire alarm system will only activate if someone in the building observes a fire and manually actuates a manual fire alarm box, often called a manual pull station. If the building is protected by an automatic sprinkler system and a sprinkler head actuates, then the waterflow switch connected to the fire alarm system will activate the fire alarm system.  

If there are automatic smoke or heat detectors connected to the fire alarm system and they are actuated, then they will activate the fire alarm system.  

Related Content: Creating a Fire Evacuation Plan

All fire alarm systems, when activated, will sound an alarm throughout the facility. NFPA 72 requires that audible notification signals be heard throughout the facility at a sound level in accordance with NFPA 72 and that visual notification appliances be seen at locations in accordance with NFPA 72. The building codes require that all buildings protected by automatic sprinkler systems have the fire alarm system transmit an alarm off-premises to an approved supervising station (monitoring or receiving station). 

Other functions that a fire alarm system will perform (and may be required by the building code or your corporate goals) include: 

• Elevator recall 
• Smoke control system activation and control 
• Smoke/fire damper control 
• HVAC unit detection and shutdown 
• Door and shutter release 
• Monitoring of other emergency systems (e.g., kitchen hood suppression) 

After sounding the alarm internally in the building and notifying the fire department through the supervising station connection, the other functions required will depend on the characteristics of the building. For example, if there are elevators present, then elevator recall and other interfaces in accordance with ASME A17.1 and NFPA 72 will be required. If there are smoke dampers, then they must be actuated by the fire alarm system. If there is a smoke control system, then its operation must be initiated by the fire alarm system. Conceivably the fire alarm system can initiate whatever other safety device or system that will help to ensure the safety of the occupants of the facility. But the actual required operations (other than occupant and fire department notification) will depend on the occupancy and local, building, and fire code requirements and on corporate fire protection goals. 

How do I determine if my smoke detectors are installed in the locations required by NFPA 72?  

Smoke detectors should be located throughout a building based on an evaluation by a fire protection engineer. To start with, NFPA 72 states in section 17.7.1.6 (2022 edition), “Smoke detectors shall be installed in all areas where required by other governing laws, codes, or standards or by other parts of this Code.”  

In some instances, the building code may specify a location for a smoke detector; the requirements of NFPA 72 only provide guidance on spacing of smoke detectors in rooms and where not to place a detector to ensure the smoke detector will not create a nuisance alarm. For example, if smoke detectors were placed on a plan without attention to ceiling height, then the detector may not provide the detection expected. If a smoke detector were placed in an area of high air flow, then detection of smoldering smoke in that area would be next to impossible.  

NFPA 72 may specify detector locations for smoke control, protection of the fire alarm control unit, or HVAC unit or damper control, but rarely for general life safety. 

Wayne D. Moore is a licensed professional fire protection engineer with over 45 years of engineering experience. Moore currently serves on the NFPA 72 Correlating Committee and Chapter 24 Technical Committee (past Chair), as well as being an editor of five editions of the “National Fire Alarm Code Handbook.”  

Larry D. Rietz, is a NICET Level IV Certified fire alarm designer with more than 29 years of life safety industry experience. Rietz is Vice President and Global Service Line Leader for Fire Detection and Alarm for Jensen Hughes and serves on the NFPA 72 Chapter 24 and 12, 21, & 23 Technical Committees.