Using a Field-Representative Controlled Testing Protocol to Assess the Detection and Quantification Capabilities of Continuous Monitoring Solutions

Fancy Cheptonui¹, Ezra Levin², Daniel Zimmerle²

¹Systems Engineering Department, Colorado State University; ²CSU Energy Institute, Colorado State University

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Background

Continuous Monitoring (CM) solutions:

  • Detect leaks more quickly and autonomously than traditional survey methods
  • Already used by oil and gas operators for internal leak mitigation

Gap:

  • Performance data not representative of field conditions and not currently well understood.
  • Need to test solutions above survey mode requirement of 15 kg/hr (EPA
  • Subpart OOOOb; EPA, 2024) (Bell et al., 2023; Ilonze et al., 2024; Cheptonui et al., 2025)
  • Future testing should include leaks from normal operational processes for representative data (Day et al., 2024)

Revised protocol developed to:

  • Evaluate solutions under field-representative conditions
  • Assess each solution against its stated operational objectives

Key updates in revised protocol:

  • Simulation of leaks from normal operational processes (“baseline emissions”)
  • Overlay of baseline and fugitive leaks
  • Updated facility structural configuration
  • Expanded test capacity
  • Evaluation aligned with each solution’s operational objectives

This study:

  • Presents results of assessing three CM solutions (Solutions A, B, and C) using the revised protocol.

Methodology

Step 1: Controlled Release of Gas

Emission types: CS-4S, CS-5S, GP, TB. Emission Rate (kg/hr) on the y-axis and Time (hours from first baseline emission of the day) on the x-axis.
Baseline emissions
Fugitive Emissions. Equipment group: 4T, 5W, 4W, 5S, 4S. Emission Rate (kg/hr) on the y-axis and Time (hours from first experiment of the week) on the x-axis.
Fugitive Emissions

Step 2: Observations Reporting

Top line: Mode 1 reporting: Solution Estimates. Arrow over to Testable Interface 1. Bottom line: Mode 2 reporting: Detection threshold and Detection. Arrow over to Testable Interface 2.

Results

Step 3: Analysis (Testable Interfaces 1 and 2)


Testable Interface 1

Sample-based quantification, Factor of 3 range: 7 to 71%. Data includes density, reported emission rate (kg/hr) and test center release rate (kg/hr).
Sample-based quantification, Factor of 3 range:

Testable Interface 1

Flowcart. Box 1: Start - Evaluation of a detection at a time step. Box 2 - Controlled Release/Reported Emission. Box 3: Cumulative Duration > Threshold Duration? Two options: Yes and No. No leads to box 4 - Threshold Value = 0. Yes leads to box 5 - Rate > Baseline, Rate + Detection, Threshold? Two options: Yes and No. No leads to box 6 - - Threshold Value = 0. Yes leads to box 7, - Threshold Value = 1.
Cumulative Mass (kg) on the y-axis and Date on the x-axis. Two lines: Test center (1063 kg) and Estimated (244 KG). Percentage error: -77%
Integrative metricAll solutions underestimated emissions. The percentage error ranged from -41 to -82
CR dataOR dataClassification
11TP
10FN
00FP
00TN
Probability of Detection (POD) on the y-axis and Release Rate above the baseline (kg ch4?h) on the a-xis.
Probability of Detection. Could not be estimated for the two solutions.
Count on the y-axis and Time to Detection (hours) on the x-axis.
Time to Detection (Range between 5.5 and 21.2 hrs)

References

  • Bell, C., Ilonze, C., Duggan, A., & Zimmerle, D. (2023). Performance of continuous emission monitoring solutions under a single-blind controlled testing protocol. Environmental science & technology, 57(14), 5794-5805.
  • Ilonze, C., Emerson, E., Duggan, A., & Zimmerle, D. (2024). Assessing the Progress of the Performance of Continuous Monitoring Solutions under a Single-Blind Controlled Testing Protocol. Environmental Science & Technology, 58(25), 10941-10955.
  • Day, R. E., Emerson, E., Bell, C., & Zimmerle, D. (2024). Point Sensor Networks Struggle to Detect and Quantify Short Controlled Releases at Oil and Gas Sites. Sensors, 24(8), 2419.
  • Cheptonui, F., Emerson, E., Ilonze, C., Day, R., Levin, E., Fleischmann, D., … & Zimmerle, D. (2025). Assessing the Performance of Emerging and Existing Continuous Monitoring Solutions under a Single-blind Controlled Testing Protocol. Elementa Sci https://doi.org/10.1525/elementa.2025.00020
  • EPA. 2024d. 40 CFR Part 60 Subpart OOOOb—Standards of performance for crude oil and natural gas facilities for which construction, modification or reconstruction commenced after December 6, 2022. Available at https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-60/subpart-OOOOb

Acknowledgments and Contact Information

This material is based upon work supported by the Department of Energy under Award Number(s) DE-FE0032276.

Fancy Cheptonui | Doctoral Student | Systems Engineering Department, Colorado State University | [email protected]

Equipment at the METEC Site