When is it necessary to install two detectors in relation to a door or double doors?

The necessity to install two detectors in relation to a door or double doors is primarily determined by the depth of any partition that may obstruct the view or access to the opening. When there is more than a 24-inch depth partition over the door, it can inhibit the effectiveness of a single detector, resulting in potential blind spots in smoke detection. The installation of two detectors helps to ensure that smoke from fires in adjacent areas can be detected without delay, enhancing the overall safety and responsiveness of the fire alarm system.

This approach aligns with the requirement to maintain effective detection in environments where architectural features—like partitions—can interfere with smoke movement. By placing a detector on either side of such obstacles, coverage is maximized, ensuring that early warning systems remain effective in the event of a fire.