When early fenceline data demands faster answers
Benzene is a regulated volatile organic compound (VOC) monitored closely under federal and state requirements. After regulatory EPA M325 data indicated elevated benzene levels at the facilities’ fenceline, the refinery team treated the signal as an operational priority. The goal was not only to understand what the data showed but to move quickly from observation to mitigative source attribution.
Instead of waiting for conditions to intensify, the refinery chose an early-action approach that balanced regulatory pressure, operational continuity and community expectations. The team partnered with Onterris to investigate in real time and build a clear pathway from detection to correction.
Moving from detection to attribution in a stepwise field strategy
The field plan focused on speed, precision and credibility. Onterris deployed a mobile Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS) laboratory, an advanced platform that detects VOCs in real time. The mobile system supported an extended survey in and around the refinery, combining ambient air monitoring with wind data and analytics designed to narrow likely emission sources.
Work progressed in defined stages to reduce uncertainty at each step:
Mobile surveys first identified benzene peaks around the fenceline and downwind areas under changing conditions.
Overnight monitoring then extended the dataset, capturing continuous readings to reflect operational and wind variability and improve confidence in pattern recognition.
Source detection algorithms translated the evolving signal into a short list of probable emission zones within the facility.
Targeted point sampling followed, allowing the team to test numerous candidate sources directly. Two sources showed significantly elevated benzene concentrations and were confirmed as high-impact release points.
This approach avoided the delays common to traditional sampling and lab turnaround, while still producing results the refinery could use to guide immediate decisions.
With PTR-TOF-MS, we moved from broad detection to pinpointing specific benzene sources in days. That pace matters under regulatory pressure because it turns data into action fast.
Turning verified results into immediate operational change
With precise source attribution in hand, the refinery team moved directly into corrective action. Process changes and focused remediation reduced excess emissions quickly, without requiring weeks of incremental sampling cycles. Just as important, the workstream created a clearer technical narrative for internal stakeholders, regulators and the surrounding community: what was detected, where it originated and what changed as a result.
Following the investigation, Onterris deployed continuous real-time fenceline monitoring using a microGC to provide ongoing, proactive surveillance. This gave the facility confidence that the issue had been resolved, while ensuring rapid notification if conditions changed.
In five days and 90 hours of monitoring, the team progressed from elevated-area signals to confirmed sources, then into action. The outcome reinforced a practical lesson for benzene programs in complex operating environments: real-time monitoring only creates value when it connects cleanly to decisions, field verification and follow-through.
A replicable model for real-time benzene monitoring in refining
This project sets a working benchmark for how refineries can shorten the path from detection to resolution. Mobile monitoring and implementing continuous monitoring can reduce uncertainty early, compress compliance timelines and support better conversations with regulators and communities when paired with a disciplined, stepwise plan.
The monitoring and verification effort is complete, with corrective actions implemented on the confirmed sources. The approach now serves as a repeatable model for future benzene investigations where speed, defensibility and operational continuity all matter.