ST3 Series Oxygen O2 Gas Sensor


The ST340 XChem Oxygen (O2) Deficiency toxic gas sensor is designed specifically to alarm when oxygen levels deviate from the ambient value of 20.9%. It provides a fast, accurate and repeatable response within a detection range of 0 to 25% oxygen. The sensor provides high specificity, fast response, and long life. Our latest design employs our “SimpleClick” sensor element replacement plus improved over-all performance and extremely low power consumption.

  • SMART Sensor Technology, Transmitter Automatically Recognizes Sensor Configuration
  • Lowest Power Consumption Available
  • Long Range (+2000ft.) Sensor Separation
  • Fine-tuned Specific Response Ensures Accurate Detection, Even In The Presence of Other Gases
  • Designed to Perform in the Most Extreme Industrial Environments
Single Channel, Dual Channel, and BASIC Transmitter Options Available   
There’s no longer the need to purchase multiple gas specific detectors. You have the option to utilize 1 or 2 toxic and/or combustible gas sensors on a single Millennium II transmitter and easily mix and match any of our sensor technologies.

SMART Sensor Technology
SMART (Self Monitoring Analysis and Reporting Technology) sensors are pre-calibrated and easily connected to the transmitter which instantly recognizes a newly fitted sensor, automatically uploading it’s specific configuration profile.


Digital Communications
Sensor and transmitter continuously communicate digitally, giving you the confidence of stable, accurate protection with fast response times even over long separation distances.

Improved Triple Electrode Design
Robust materials have been utilized on Sensing, Reference and Counter electrodes within the ST3 sensing element which ensures long-life and enhanced performance.

Advanced Environmental Immunity
The ST3 Series of toxic gas sensors are all internally temperature-compensated to their particular target gas and field-selected range in order to provide as stable a sample as possible to the sensing element. Humidity is also controlled through the use of an advanced diffusion process as gases pass through our specialized hydrophobic barrier.


Global Certifications
The ST3 Series has been approved to international hazardous area safety standards.

OXYGEN [O2] (Electrochemical)
P/N: ST340(A/S)-25-ASSY

Response Time: T20 ≤ 8 sec | T50 ≤ 10 sec | T90 ≤ 20 sec
Accuracy: (+/–) 3% Full Scale
Detection Range: 0­­—25% Oxygen
Zero Drift: < 5% per year
Repeatability: < 3% full scale
Temperature: -20°C to +50°C (-4°F to 122°F)
Relative Humidity: 5–95% RH non condensing
IP/NEMA Rating: IP64 – NEMA 4X
Metallurgy: Aluminum or 316 SS
Sensor Separation: Up to 2000 feet/600 meters (18 AWG cabling)
Transmitter Req’d: Millennium II Series (M21, M22, M2B)
Warranty: 2 years
Price: $0.00