When are two ceiling-mounted detectors required for door release service?

Two ceiling-mounted detectors are required for door release service when the depth of the wall section above the door exceeds 24 inches. This requirement is in place to ensure that the smoke or heat from a fire is effectively detected before it enters the room or area behind the door.

When the wall section above the door is deeper than 24 inches, it can obstruct the effective detection of smoke or heat, which could threaten life and property. By utilizing two detectors in this scenario, the system increases the likelihood of timely detection, ensuring the door release mechanism is activated appropriately to facilitate safe evacuation or alerting.

The other options do not fulfill this specific criterion, as the width of the door or whether it is electric does not influence the need for additional detectors based on the architectural features present. Understanding these regulations is crucial for fire safety protocols and ensuring compliance with relevant codes.