I posted this photo a loooong time ago, and this issue has come up several times lately. When I took the photo, the sensor did not unlock the electromagnetic lock until I actually touched the door and the movement of my hand triggered the sensor. It seems obvious that the sensor should not be positioned behind the exit sign (or any obstruction), but when the issue is pointed out to the facility manager, he or she will often ask where they can find the guidelines for sensor placement.
Taking a step back to make sure we’re all on the same page…there are two code sections that address electromagnetic locks in order to allow free egress. One section covers electromagnetic locks that are released by hardware that’s mounted on the door – like panic hardware with a request-to-exit (RX) switch. The other section covers electromagnetic locks that are released by a sensor which detects an approaching occupant and unlocks the door. Both sections include other requirements, and there is more information in this article.
In NFPA 101 – The Life Safety Code and editions of the International Building Code (IBC) prior to the 2015 edition, the section that addresses the mag-lock application with the sensor is called Access-Controlled Egress Doors. Because there was confusion about whether this section applies to every door with an access-control reader (it doesn’t!), the name of the section was changed in the 2015 edition of the IBC. It is now called Sensor Release of Electrically Locked Egress Doors.
With this type of system, NFPA 101 and the IBC require a sensor which detects an approaching occupant and unlocks the door. With regard to the sensor, the IBC says: “The sensor shall be installed on the egress side, arranged to detect an occupant approaching the doors. The doors shall be arranged to unlock by a signal from or loss of power to the sensor.” NFPA 101 says: “A sensor shall be provided on the egress side, arranged to unlock the door leaf in the direction of egress upon detection of an approaching occupant.”
I am positive that the intent of this requirement is for the mag-lock to release AS SOMEONE IS APPROACHING THE DOOR, not when someone runs into the still-locked door and they are finally detected by the sensor. But the codes don’t currently include prescriptive requirements as to the type of sensor, the detection range, or the timing of the door release. When a facility manager asks me for evidence of why it’s not acceptable for the door to remain locked until someone is standing under the sensor touching the door or waving at the sensor, all I have is the code language above.
Here’s my question for you. Other than common sense and an understanding of what the likely intent of the code is, what else can I use to demonstrate any sort of standard pattern for the sensor’s detection area? Any best practices or default detection zones? Patterns that show up in the installation instructions for various products? The 2015 IBC Commentary supports my opinion that the door should unlock when the occupant is APPROACHING the door (not standing at the door):
“Item 1 requires that such doors be provided with an occupant sensor on the egress side of the door. These sensors typically operate on an infrared, microwave or sonic principle, but other technologies may be available. This sensor is required to automatically release the electrical lock on approach of an occupant from the egress side or when there is a loss of power to the sensor. This provision is written as “performance-based,” where any means of sensor design can be utilized to cause the doors to unlock, allowing immediate egress. This section does not indicate at what distance the sensor should be set to operate. The sensor may be set to detect an approaching occupant in time to unlock the electrical locks prior to the occupant reaching the door, to permit egress without the occupant realizing the doors were electrically locked. In other applications, the sensor may be set to require the occupant to be closer to the door prior to unlocking the electrical lock to allow egress.”