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Ethylene Oxide Monitoring

CleanAir’s MET-44 Line of Products introduces Next Generation Emission Measurement (NGEM) solutions for the industrial monitoring of Ethylene Oxide (EtO or EO). Based on Cavity Ring-Down Spectroscopy (CRDS), all of CleanAir’s EtO monitoring solutions generate accurate and defensible data down to ultra-low levels. 

MET-44 configurations include ethylene oxide Continuous Emissions Monitoring Systems (MET-44 CEMS) as well as indoor, and outdoor fenceline, and leak detection monitoring configurations (MET-44 aQ). The same underlying technology from the MET-44 CEMS and MET-44 aQ is used by CleanAir to conduct mobile site surveys for clients interested in characterizing ethylene oxide concentrations throughout and around any facility.

Thanks to CleanAir’s focus on system reliability and availability, data quality and reporting, as well as CleanAir’s best-in-class support services, the MET-44 system line-up and related services have quickly become the premier ethylene oxide monitoring solution on the market. 


  • Reliable Performance
  • High Data Availability
  • Generation of Defensible Data
  • Performance Specification 19-Compliant
  • Comprehensive and Custom Reporting Solutions


  • Ultra-Low Detection Limit: 250 ppt
  • Rapid System Response Time: <10 seconds
  • Measurement Interval: <5 seconds
  • Fully Integrated within MET-44 Line of Products


  • 50+ Years of Providing Unsurpassed Support Services
  • Comprehensive 24/7 Customer Support
  • Annual or On-Demand Support Service Programs
  • Fully Documented System Performance
  • Highly Experienced Support Team

Continuous Emissions Monitoring Systems

Accurately quantifying facility emissions and documenting larger than 99.99% reduction efficiencies of air pollution control equipment requires a measurement technology that is capable of quickly and reliably detecting ethylene oxide at sub-parts-per-billion (ppb) concentrations. The MET-44 EtO CEMS, built around CRDS technology, provides enhanced accuracy, precision, sensitivity, and rapid response. The MET-44 CEMS and its high-quality sampling system components developed by CleanAir is the most state-of-the-art ethylene oxide continuous emissions monitoring solution available on the market. Complemented with a regulatory reporting package that comes as part of the system, the MET-44 CEMS assures the generation of defensible and well-documented data by providing a submission-ready compliance reporting solution.

  • Built-to-Order Sampling Probes and Heated Sampling Lines
  • Fully Automated System Operation and Calibrations
  • Integration of Industry-Proven Stack Gas Flow Monitoring Technology
  • Performance Specification 19 – Compliant Operation and Reporting
  • Capable of Documenting >99.99% Reduction Efficiencies
  • Time-Share Enabled Emissions Monitoring

Indoor Air Quality Monitoring


The MET-44 aQ is CleanAir’s solution for the reliable monitoring of indoor air quality. The MET-44 aQ system is versatile and can be implemented in a wide variety of applications including industrial hygiene or employee exposure monitoring, upgrades to aging systems, or laboratory-specific applications. Paired with a scalable and patent-pending multi-point sampling approach, the MET-44 aQ allows a facility to rapidly cycle through 48 locations in less than 24 minutes! And with its fully-automated system performance verification and calibration feature, the MET-44 aQ generates data with accuracies that can be traced to established reference standards.

  • Industrial Hygiene, Baseline, or Site-Specific Applications
  • Rapid Multi-Point Sampling of up to 48 Points
  • Automated Calibration Verifications to Ensure Data Defensibility
  • Customizable Reporting and Visualization Capabilities

Fenceline Monitoring

Characterizing ethylene oxide levels at facilities’ fenceline requires an ultra-high sensitivity measurement paired with a rapid system response. CleanAir’s solution, the MET-44 aQ, satisfies both requirements. It is based on CRDS technology combined with CleanAir’s patent-pending rapid multi-point sampling approach. The MET-44 aQ’s open integration approach allows for interfacing with third-party sensors as well as meteorological measurement systems to identify potential fugitive emission sources as they occur. Combined with support services that include planning, reporting, as well as associated consulting, CleanAir’s MET-44 aQ can address any ambient and fenceline monitoring system and project needs. 

  • Parts-Per-Trillion (ppt) Level Detection Limit
  • Scalable Rapid-Response Multi-Point Sampling System
  • Fully Automated System Operation and Calibration
  • Remote Cloud-Based Data Management
  • Quality Assurance Project Plan Development
  • System Support and Reporting Services
  • Fully Integrated and Alarming Light Towers
ethylene oxide facility sensor for fenceline

Mobile Monitoring

mobile monitoring jeep

CleanAir offers mobile monitoring for ethylene oxide and other target compounds via our mobile monitoring fleet of Jeep Gladiators! Each Jeep Gladiator is equipped with advanced CRDS technology, transforming it into an offroad-ready precision monitoring platform. Complemented with geotagged mobile meteorological measurements, this allows for the rapid generation of sensitive, real-time data that can be used to map concentration profiles within or at facility fencelines and readily identifies potential fugitive emissions sources. The Jeep is a great option for ethylene oxide monitoring.

  • Sensitive Mobile Measurements
  • Geotagged Meteorological and Concentration Data
  • Turnkey Monitoring Project Services
  • Facility Concentration Profiling
  • Source Characterization
  • Monitoring Project Plan Development

Leak Detection & Repair

As part of U.S. EPA’s NGEM initiative, regulatory agencies have investigated the approach of using localized continuous measurements as an alternative to existing Leak Detection And Repair (LDAR) requirements. The framework for this approach is known as Alternate Means of Emission Limitation (AMEL), which is defined in the Clean Air Act and allows an entity to petition the U.S. EPA to allow an alternative compliance approach to a federal air standard provided that the proposed alternative achieves equivalent or greater emissions reduction relative to the existing standard. The MET-44 aQ’s versatile rapid multi-point sampling coupled with highly sensitive EtO detection is a great fit for the AMEL approach, making it a perfect tool for continuously detecting and identifying leaking equipment within affected facilities. This measurement approach was featured in a recent article published in the scientific journal Atmospheric Environment: X.

  • Scalable Rapid-Response Multi-Point Sampling System
  • Fully Automated, Unattended System Operation and Calibration
  • Integrated Alarming and Messaging for Rapid Maintenance
  • Earlier Leak Detection Compared to Non-Continuous Methods
  • Monitoring and Response Plan Development
  • System Support and Reporting Services
atmospheric environment X journal cover

Regulatory Compliance Testing

To enable our industrial clients to apply the most robust ethylene oxide monitoring and measurement technology on the market for their regulatory compliance testing needs, CleanAir completed a U.S. EPA Method 301 technology validation that is specific to the application of CRDS for EtO testing at sterilization facilities. With the publication of OTM-47 (Measurement of Ethylene Oxide Emissions from Stationary Sources by Cavity Ring-Down Spectroscopy), CRDS can now be used for regulatory compliance and EtO CEMS performance verification measurements. And with the quality assurance framework established in OTM-47, CleanAir can now generate robust and reliable data that can be used with high confidence in engineering studies and in evaluating and optimizing air pollution control systems.


  • EtO Measurements with Parts-Per-Trillion (ppt) Level Detection Limits
  • High Confidence Data for Performance Evaluations
  • Capable of Documenting >99.99% Removal Efficiencies
  • Professional and Reliable Testing Services
  • On-Time Reporting