Siemens OH921


Addressable Multi-Criteria Fire Detector

Availability: Estimated 6 - 8 Business Days

  • Factory New
Brand: Siemens Part #: 49125 Categories: , Manufacturer Part #: OH921Secondary Part #: S54320-F6-A2


The Photoelectric | Thermal (Heat) Detector (Model OH921) is an intelligent, addressable multi-criteria detector that incorporates optical and thermal sensors, and uses signals in a neural network to create an intelligent multi-criteria detector. The encompassing result is a detector that provides enhanced detection to a wide range of products of combustion.

Model OH921 is UL 268 7th Ed. listed and incorporates advanced built-in isolation (optionally configurable), which greatly improves reliability, circuit integrity and provides advanced addressable fault finding.


Weight 0.32 lbs
Dimensions 2.00 × 4.50 × 4.50 in

Siemens Industry, Inc.





Unit of Measurement

EA (Each)



Detection Method

Fixed Temperature, Photoelectric, Programmable, Rate-of-Rise

Thermal Rating


Production Status



  • UL 268 7th Edition Listed
  • Built-in isolation (optional configurable)
  • Each detector is self-testing:
    • complete diagnostics performed every 10 seconds
    • self-monitored for sensitivity within UL Listed limits
  • Listed, approved as a heat detector:
    • Rate-of-Rise Detection: 15°F / min. (8.3°C / min.)
    • Fixed: 135°F (57°C)
  • Superior electromagnetic interference (EMI) and radio-frequency interference (RFI) immunity
  • Field programmable as rate-of-rise or fixed temperature, per ‘Alarm Source 2’ | Standard parameter
  • Tri-color detector-status light-emitting diode (LED) with 360° view
  • Compatible with Model 8720 | DPU (device programmer / loop tester)
  • Polarity insensitive via SureWire technology (in non-isolator mode)
  • Functions with Model DB-11–series mounting bases
  • Restriction of Hazardous Substances (RoHS compliant)
  • Automatic environment compensation
  • UL Listed | FM, CSFM Approved
    • UL 268: `Open Area Smoke Detection’
    • UL 268A (Duct) – `Direct-in-Duct’ use
    • UL 521: `Open Area Heat Detection’
    • ULC-S531: `Open Area Smoke Detection’
    • ULC-S539: `Open Area Heat Detection’
    • FM 3230: `Open Area Smoke Detection’
    • FM 3210: `Open Area Heat Detection’
    • CSFM | File: 7272-0067:0258

Model OH921 Multi-Criteria Fire Detector

Siemens - Data Sheet

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