Where should a smoke detector be installed to automatically close a double doorway in response to smoke?

Installing a smoke detector on the centerline of a doorway is the most effective placement for ensuring optimal detection of smoke and triggering a response, such as automatically closing a double doorway. This position allows the smoke detector to monitor the airspace directly above and within the threshold of the doorway, where smoke from a fire is likely to accumulate first.

Smoke detectors are designed to sense the smoke particles in the air, and positioning it at the centerline height means it will be able to detect smoke rising from a fire that may start nearby. This prompt detection is critical for implementing life safety measures such as closing doors to contain smoke and fire spread, thereby protecting occupants and enhancing evacuation routes.

In contrast, other placements, like next to the doorway or on the ceiling above but not focused directly on the doorway, may not offer the same level of monitoring efficiency. For instance, smoke rising may not trigger a detector mounted too low to the wall or poorly oriented relative to the smoke's path, potentially delaying critical response mechanisms that rely on timely smoke detection.