Presence Detectors are designed for automatic ventilation control of HVAC systems. It uses infrared light. The detector has a potential-free change-over relay for activation/deactivation of for instance a fan-coil controller. It saves money and gives higher comfort in premises requiring forced ventilation for shorter periods of time, such as conference rooms, assembly-halls etc.
Smoke detectors are intended for mounting on all duct types. They react on visible and invisible smoke particles and can therefore detect fire at an early stage.