Oxygen analyzer and sensor solutions for air separation units, PSA/VPSA nitrogen and oxygen generators, cryogenic air separation plants, industrial gas cylinder filling, and gas purity verification applications.
Air separation and industrial gas production are among the most measurement-intensive processes in modern industry. Whether you are operating a large cryogenic air separation unit (ASU), a pressure swing adsorption (PSA) nitrogen generator, a vacuum pressure swing adsorption (VPSA) oxygen plant, or a cylinder filling station, accurate oxygen measurement is essential at every stage of production, purification, and distribution.
Oxygen analyzers serve two distinct and equally critical roles in these applications. In nitrogen and inert gas production, oxygen measurement verifies that the product meets purity specifications and is free from residual oxygen contamination. In oxygen production and enrichment applications, analyzers confirm that product concentration meets the required grade — whether for industrial, medical, or specialty gas use.
This application note covers the major oxygen monitoring requirements across cryogenic air separation, PSA/VPSA gas generation, cylinder filling, and industrial gas distribution operations, and identifies which Southland Sensing analyzers and sensors are best suited for each stage of the process.
Why oxygen monitoring matters: Continuous or intermittent oxygen measurement at critical process points confirms product purity, prevents off-specification gas from reaching customers or downstream processes, detects air ingress into nitrogen and inert gas systems, and protects personnel from oxygen-deficient or oxygen-enriched atmospheres in production and storage areas.
OMD-675
The OMD-675 is the standard choice for continuous online oxygen monitoring in PSA nitrogen generators, cryogenic ASU product streams, and gas purification systems requiring sub-ppm sensitivity. Full-featured rack-mount transmitter with 4–20 mA output and Modbus RTU for SCADA / DCS integration. Ideal for plant control rooms monitoring multiple production streams simultaneously.
OMD-740
Designed specifically for high-concentration oxygen measurement with suppressed ranges for accurate reading in oxygen-enriched streams. The ideal solution for VPSA and cryogenic oxygen production verification, medical oxygen quality control, and cylinder filling station QC where product oxygen concentration must be confirmed within a tight, defined range.
✓ Suppressed Ranges · Purity-Optimized
OMD-640
Compact and portable — ideal for spot-checking PSA generator outlet purity, commissioning new gas generation equipment, troubleshooting suspected air ingress, and verifying cylinder contents during filling operations. Where permanent installation is impractical or multiple sample points require periodic verification, the OMD-640 delivers laboratory-grade accuracy in the field.
OMD-507
Space-saving in-line transmitter suited for skid-mounted PSA/VPSA generation units, compact nitrogen generator packages, and gas blending skids where panel space is limited but continuous online measurement is required. Same measurement performance as larger models in a compact housing designed for easy integration into OEM equipment.
✓ Configurable · OEM-Ready Design
Accurate oxygen analysis in air separation and industrial gas applications depends not only on the analyzer selected, but also on a properly designed sample conditioning system. Gas streams in these applications may contain moisture, trace hydrocarbons, particulates from molecular sieve beds, and pressure differentials that must be managed before the sample reaches the analyzer cell.
For trace oxygen measurement in nitrogen and inert gas streams, sample system cleanliness is especially critical — even small leaks in the sample tubing or fittings can introduce ambient air contamination and produce falsely elevated readings. All sample system connections should be leak-tested and wetted materials selected for compatibility with the process gas and expected trace contaminants.
For high-concentration oxygen streams (VPSA/ASU oxygen production), sample systems must be constructed from materials compatible with oxygen service to prevent combustion hazards. Cleanliness of all wetted components is mandatory in oxygen-rich service.
Southland Sensing provides application engineering support to help customers specify appropriate sample handling systems for both trace and percent-range oxygen measurement in air separation and gas generation applications. Contact the factory to discuss your process pressure, flow conditions, moisture content, and installation requirements.
Oxygen-deficient and oxygen-enriched atmospheres both present serious and potentially fatal hazards in industrial gas production facilities. Liquid nitrogen, liquid argon, and other cryogenic inert gases can rapidly displace oxygen in enclosed spaces, creating life-threatening hypoxic conditions with no visible warning. Conversely, liquid oxygen storage and distribution areas present a fire and explosion risk from oxygen enrichment.
Fixed ambient monitors should be installed at appropriate elevations throughout all enclosed production buildings, cylinder storage areas, liquid gas storage rooms, and filling stations. Our OMD-351 series monitors provide continuous room-air O₂ measurement with audible and visual alarms at user-configurable setpoints (typically 20.0% for high oxygen warning and 19.5% for low oxygen alarm), supporting compliance with OSHA and local facility safety requirements.
Refer to our O₂ Sensor Compatibility Guide to confirm the correct sensor for your analyzer model and process application.
Our application engineers assist with sensor selection, installation, and hazardous area questions.
Our application engineers are available to assist with sensor selection, installation guidance, and hazardous area classification questions for your hydrogen production system.
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