Siemens OH121 Photoelectric Smoke and Thermal Detector

The Siemens OH121 Photo Thermal Smoke Detector combines a photoelectric smoke sensor with a thermal element in a single conventional detector, designed for use with non‑addressable Siemens fire control systems in commercial spaces. As a conventional (non‑addressable) detection device, it delivers rapid smoke detection with an integrated 135°F (57°C) thermal threshold to help confirm heat conditions and reduce nuisance alarms. Local visibility is enhanced by a three‑color LED that indicates sensitivity status, and a magnet test feature lets technicians verify operation quickly without special testing tools. The OH121 includes internal self‑diagnostic circuitry that continually verifies sensitivity and function, supporting reliable performance over time, and it offers optional remote LED indicators and an optional sounder base for enhanced signaling. The device is UL 268 listed, ULC S529 listed, and CSFM approved, reflecting compatibility and compliance across major safety jurisdictions. In Siemens’ product lineup, OH121 is cataloged as S54372‑F2‑A1 (conventional photo/thermal detector) and sits alongside other conventional detectors in the OP121/HI121 family, illustrating its role as a plug‑in, ceiling‑mounted detector for standard fire alarm panels. Typical applications include offices, retail environments, and educational facilities where fast smoke detection is combined with thermal confirmation to support prompt and reliable fire response within existing Siemens fire safety systems.