A delayed egress lock is a device which prevents egress for a period of time, while sounding an audible alarm. The typical time delay is 15 seconds, although a 30-second delay is allowed if approved by the Authority Having Jurisdiction (AHJ). There are other criteria that must be met, like signage, emergency lighting, and immediate release upon fire alarm (there are more criteria listed here).
To initiate the 15-second timer, a force of not more than 15 pounds must be applied for up to 3 seconds, according to the 2015 International Building Code (IBC) and NFPA 101 – The Life Safety Code. Prior editions of the IBC required a 1-second application of force.
The way I’ve always interpreted this is there is an initiation time of 1-3 seconds (depending on the device settings), plus the 15 seconds to release the device, or a total of up to 18 seconds between the time a building occupant reaches the door and the time they’re able to open the door and exit. Recently someone mentioned that the AHJ used a stop-watch to time the cycle on their delayed egress hardware, and said that because the total time was more than 15 seconds (it was 18 seconds), it was a violation.
I checked with the ICC and NFPA for a code opinion, and both staff members acknowledged that the codes do not address this specific issue, so it would be left up to the AHJ. One made a good point – the time to initiate the timer and the time to release the device should be two separate periods (for a total of 18 seconds, maximum) because the initiation time could be 1, 2, or 3 seconds. If the code required a total time of 15 seconds, then the release time would have to compensate for the initiation-time settings, and release after 14, 13, or 12 seconds. That would be complicated, and we’re talking about 3 seconds here – probably not a life-or-death issue.