Chemical manufacturers face increasing compliance demands as the EPA’s HON MACT rule updates will require fenceline monitoring through Method 325 sampling. Facilities that haven’t historically been subject to these requirements must now prepare for significant operational, logistical, and technical changes.
The proposed 2026 compliance deadline is accelerating the need for action. Method 325, a standardized procedure that involves placing passive air samplers around facility boundaries to measure benzene emissions over time, was originally developed for refineries and required industry-wide in 2018, is now expanding to include a broader range of facilities. Lessons learned from the refinery sector reveal just how complex and nuanced Method 325 sampling and implementation can be.
This blog shares hard-earned lessons from years of Method 325 implementation in refineries—lessons that chemical manufacturers can begin applying today as they prepare for upcoming HON MACT requirements. It highlights key insights around field execution, lab coordination, and communication protocols that have proven critical to success.
The Road to Method 325 Expansion
Method 325 was finalized in 2015 for refinery fenceline monitoring and became fully enforceable by 2018. Since then, its scope has gradually expanded beyond the refining sector. In 2023, the EPA proposed updates to the Hazardous Organic NESHAP (HON MACT),), formally extending the requirement to chemical manufacturing facilities. With enforcement proposed to begin in 2026, this marks a significant shift in air monitoring expectations across the sector.
But this is far from plug-and-play solution. Method 325 requires biweekly passive tube sampling, data review and validation, laboratory analysis, and continuous system oversight. Each component must work in harmony, something that took refineries years to get right.
Why Execution Matters: Lessons from the Field
One of the biggest lessons from the refining sector’s experience is clear: field execution makes or breaks fenceline monitoring. While the process may seem straightforward, deploy a tube, collect it two weeks later, and analyze in the lab, there are countless opportunities for data quality to degrade without proper coordination and training. In one case study, a refinery experienced erratic results due to improperly tightened tubes, an easy error with costly repercussions. Once field teams were trained on proper torque specs and QA/QC protocols, the data quality stabilized. Another key lesson involves process timing: delays in shipping, deployment, or lab analysis compromise data integrity and risk meeting regulatory deadlines. To mitigate these risks, labs must work with their project partners to develop contingency plans, such as faster return shipping and maintaining a larger equipment inventory.
Equally important is the role of detailed field technician notes. These notes provide valuable context—such as observations about weather conditions, site activities, or equipment anomalies——that provide essential context for the lab. This information helps troubleshoot anomalies, prevent wasted analyses, and avoid instrument downtime. In many cases, field notes have helped identify and resolve issues before they impact results, ensuring more reliable and actionable data.
The Lab’s Role in Compliance Success
What happens once the tubes return to the lab is just as critical as what happens in the field. Labs must manage variable sample loads, data turnaround pressures, and close coordination with clients. Method 325 doesn’t just test a facility’s emissions—it tests the strength of its relationships with its lab partners.
Frequent miscommunications between field teams, clients, and labs created delays and confusion. But when weekly syncs were introduced and expectations were clearly defined from the start, these issues began to fade. Clear communication channels and mutual accountability were among the most impactful improvements seen across successful programs.
Scaling for HON MACT: Chemical Plants, Take Note
Unlike the refining sector, many chemical manufacturing facilities lack the infrastructure and institutional knowledge to scale up for Method 325. As enforcement approaches, compliance will require more than just procuring samplers and hiring a lab—it demands a coordinated, site-wide readiness strategy, including:
- Developing internal SOPs for deployment and collection
- Training field staff to reduce sampling variability
- Establishing proactive communication with labs
- Stress-testing operational timelines to avoid regulatory lapses
Facilities should also begin piloting sampling processes now to troubleshoot gaps before the rule takes effect. Early adoption allows for system tweaks, staff upskilling, and vendor alignment, without the pressure of a looming compliance deadline.
Conclusion: Lessons Learned, Actionable to Take Now
EPA Method 325 isn’t just a compliance box to check. It’s a complex, multi-part system that requires precision, coordination, and foresight. The refining industry’s experience with Method 325 offers valuable insights chemical manufacturers can act on today—if they start early and invest in operational readiness.
Key takeaways:
- Field execution errors, even minor ones, can compromise data integrity.
- Strong coordination between labs and clients is essential to avoid delays and compliance risks.
- Clear communication protocols are one of the most effective tools for program stability.
- Facilities should begin preparation now to stay ahead of the steep curve as proposed HON MACT enforcement approaches
Interested in building an effective HON MACT Method 325 sampling program? Get in touch to learn how we can help.
For more resources and expert insights, visit our HON MACT Insights hub.