Which detectors may be recessed in the mounting surface if listed and tested for that purpose?

• A. CO detectors
• B. Smoke or heat detectors
• C. Motion detectors
• D. Glassbreak detectors

Answer: (B)

Recessed mounting is allowed only for devices that are specifically listed and tested for that installation method. Smoke and heat detectors often have recessed versions that are designed to fit flush with a ceiling or wall while still allowing adequate airflow to the sensing element. When a model is listed for recessed mounting, the manufacturer has verified that it will operate correctly, stay accessible for maintenance if needed, and meet clearance and venting requirements.

Other detectors aren’t typically designed or listed for recessed installation. CO detectors are generally meant to be surface-mounted for accessibility and maintenance reasons, and their sensing and venting needs aren’t typically compatible with a recessed housing. Motion and glassbreak detectors rely on an unobstructed field of view or vibration path, so enclosing them within a mounting surface would interfere with their sensing and is not standard practice or listed for recessed use.

So, only smoke or heat detectors have recessed versions that are listed and tested for that purpose.