Use of Open Path UV-DOAS

Use of Open Path UV-DOAS as an Alternative Method to Meet Fence-line Monitoring Provisions for Federal Benzene Monitoring Rule; A Case Study 

By Mark Wicking-Baird, Argos Scientific Africa Inc.

On December 1, 2015, the EPA finalized the Risk and Technology Review for petroleum refineries.  Among other things, the finalized rule requires petroleum refineries to conduct fence-line monitoring on a continuous basis.  Benzene was defined as the target compound, and an annual average, action level of 9 µg/m3 was established, triggering a refinery lead root cause analysis and corrective action. The fence-line monitoring provisions found in 40 CFR 63.658 describe the use of a network of passive diffusive tube samplers placed along the refinery's boundary as the primary method for detecting fugitive emissions of benzene.

The fence-line monitoring provisions allow a refinery owner or operator to submit a request for an alternative test method, such as the use of open-path instrumentation. The use of this type of technology presents the opportunity to meet the requirements of the rule in a more simplified and cost-effective way, while offering advantages in terms of time resolution and potentially identifying and eliminating data points that correspond to non-facility emission sources.  A field validation study has been conducted using latest generation, open-path UV-DOAS technology to detect benzene at a refinery fence line on a continuous basis. This study includes the development of a quality assurance program that is compliant with the ISO-17025 standard for the operation of a gas analyzers as a field analytic laboratory. The analysis includes a case study on the lessons learned in developing this program, and presents a path forward in utilizing the open-path fence-line monitoring systems installed at refineries in California to meet the federal fence-line rule for benzene monitoring.