System Sensor D4120 4-Wire Photoelectric Low-Flow Duct Smoke Detector, 24VDC/120VAC, (Replaces DH100ACDCLP)

Protect building occupants and critical equipment with the System Sensor D4120 4-wire photoelectric low-flow duct smoke detector, engineered for reliable HVAC and duct monitoring in commercial security and life-safety systems. The InnovairFlex D4120 delivers dependable early smoke detection across airflow speeds from 100 to 4,000 feet per minute and withstands temperatures from -4°F to 158°F, making it ideal for varied ductwork environments. Its plug-in sensor head and patented sampling tube allow tool-free installation and straightforward maintenance, minimizing downtime for facilities and service teams. With integrated low-flow technology, improved false-alarm immunity, and support for 24VDC/120VAC power, the D4120 integrates seamlessly into fire alarm, building automation, and security surveillance setups. The detector’s interconnect feature enables coordinated multi-fan shutdown to limit smoke spread during incidents, enhancing overall system response. UL-listed and purpose-built for commercial HVAC protection, the System Sensor D4120 is a practical choice for contractors, integrators, and building managers who require robust monitoring and simplified maintenance. Order the D4120 for reliable duct smoke detection and improved HVAC safety performance.

• Reliable duct protection with low-flow photoelectric sensing for early smoke detection and reduced false alarms
• Handles challenging HVAC conditions: operates at 100–4,000 fpm airflow and -4°F to 158°F for broad application coverage
• 4-wire design with 24VDC/120VAC support for flexible integration into existing life-safety and security systems
• Plug-in sensor head and front/back sampling tube for fast installation, testing and low-maintenance servicing
• Patented multi-fan shutdown interconnect for coordinated HVAC fan control and faster event response
• UL-listed and built for commercial environments, helping simplify code compliance and system monitoring