The proposed Appendix K rule seeks to establish requirements for the optical gas imaging (OGI) camera, equipment, and supplies needed to complete OGI surveys, including the initial performance verification of the camera and developing operating envelopes. The following sections provide a summary of those requirements, along with how this could impact OGI surveys.
Camera Requirements
The OGI camera must meet the following specifications:
- The spectral range of the infrared radiation measured by the OGI camera must overlap with a major absorption peak for the chemical of interest.
- The camera must be capable of detecting methane emissions at 17 grams/hour (g/hr) and butane emissions at 18.5 g/hr at a distance of 2 meters with a delta-T of 5 °C and calm winds (1 meter per second (m/s) or less).
- The inherent ability of most OGI cameras to detect gases is not influenced by the calibration process, and will not degrade over time.
These requirements are industry standards for OGI cameras and should not affect survey procedures.
Initial Performance Verification Equipment and Supplies
The following equipment is needed to provide initial performance verification of the OGI camera:
- Calibration gases with mass flow controller
- Variable speed industrial fan
- Meteorological station (ambient temperature, pressure, wind speed, wind direction, relative humidity)
- Temperature-controlled background
- Thermocouples
- Device to measure distance from camera to release point
This equipment is not only used for the initial performance verification but will also be required for developing operating envelopes in addition to being onsite to document that site conditions are within established operating envelopes prior to conducting surveys.
The proposed requirements will result in increased costs for conducting OGI surveys due to additional equipment costs and limiting travel to driving distances due to the amount of equipment required for a survey.
Developing Camera Operating Envelope
The operating envelope for an OGI camera can be affected by viewing distance, wind speed, air temperature, and background temperature. Development of an operating envelope is to be performed using the calibration gases with a mass flow controller (methane at 17 g/hr, then butane and 18.5 g/hr) and varying delta-T, viewing distance, and wind speed. For each combination of these variables, a panel of no less than 4 observers with demonstrated capability of detecting gaseous leaks will observe the test gas release. A detected emission is determined when 3 of the 4 observers see the leak.
The operating envelope that will be used for the survey is the more restrictive test using either methane or butane as calibration gases and the aforementioned variables. This process is to be repeated for each camera configuration (e.g., high sensitivity, available lenses, and handheld vs. tripod) that will be used in the field. The results of the testing to establish the operating envelopes, including the supporting videos, must be documented and maintained with other OGI records.
This process for developing operating envelopes is anticipated to be costly in time and equipment because the proposed method requires the camera operator to replicate all conditions encountered during a survey. Additionally, this recordkeeping requirement will require large amounts of data storage capacity that may present a challenge to many stakeholders.
Up Next
Stay tuned for the next article in our series, which will focus on the training requirements proposed in Appendix K.
If you missed our last article, you can catch up here.
Key Dates
- November 15, 2021: Proposed rule published
- November 30, 2021, and December 1, 2021: Virtual Public Hearing
- December 15, 2021: Comments due on the information collection provisions for consideration by the Office of Management and Budget (OMB)
- January 31, 2022: Comments due to EPA
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