What type of back box is required for mounting a flush-mount PIR?

A single-gang electrical box is specifically designed to accommodate devices like a flush-mount PIR (Passive Infrared) sensor, which typically requires a compact space to fit properly against walls or ceilings. These sensors are designed to detect motion based on changes in infrared radiation and are often installed in areas where they can monitor movement effectively.

Using a single-gang box ensures that the sensor is securely mounted and positioned correctly for optimal performance. This type of back box provides sufficient space for the wiring connections associated with the PIR while maintaining a low profile against the flush surface. In contrast, a double-gang or triple-gang box offers unnecessary additional space, which is not suited for the streamlined installation of a PIR, and could hinder its aesthetic and functional integration into the environment. A surface-mount electrical box is generally used for installations where fittings are on the outside of walls, which is not appropriate for flush-mount applications.