“Do I need smoke detectors at doors on magnetic hold opens?” This is a frequently asked question by designers who are faced with the challenge of creating open circulation in portions of buildings where doors are required for fire protection purposes. A common solution for this problem is to put those doors on magnetic hold opens so they don’t interrupt these circulation paths and site lines unless there is a fire condition where they need to be closed. Unfortunately, the installation of the magnetic hold opens isn’t as simple as installing the magnets and connecting them to the fire alarm system such that they close on activation. A compliant arrangement also requires examination of the location of the detectors themselves which tell those magnets to release the doors so that they will shut in a fire condition.
Unfortunately, the answer to where to install those detectors is “it depends”.
The International Building Code as well as NFPA 101, the Life Safety Code, references NFPA 72, National Fire Alarm Code where you can find the detailed requirements for installation of smoke detectors. Chapter 17 Initiating Devices of NFPA 72 provides compliant options for smoke detector layouts for door release devices including various ceiling height scenarios.
Option 1:
The first option is to utilize complete area detection, where the entire space (i.e. corridor) is protected throughout by smoke detectors that are commonly spaced at 30-foot intervals. This option does not require any special detectors near the doors since they will be told to close if a smoke detector anywhere in the department is triggered.
Option 2:
Option 2 uses an approach where it only requires a detector or detectors near the hold open door. The challenge here is that the header depth above the door can create different airflow patterns for smoke to travel across the door. To ensure detection will be located in an area where smoke is likely to exist, NFPA 72 has varying requirements on if the detectors are needed on one side of the door or both, depending on that header depth. Section 17.7 Smoke-Sensing Fire Detectors of NFPA 72 has a table (Figure 17.7.5.6.5.1(A)) that designers can use to locate the detectors properly.