In response to growing concerns over hazardous air pollutants, the U.S. Environmental Protection Agency (EPA) has finalized new requirements under the Hazardous Organic NESHAP (HON) regulations. These updates impact hundreds of petrochemical manufacturing facilities across the country, including new mandates for fenceline monitoring of ethylene oxide (EtO). Non-compliance with these regulations could result in significant penalties and potential damage to a facility’s reputation.
According to AFPM, there are 311 petrochemical manufacturing facilities in the United States. Of these, approximately 200 fall under the scope of the amended HON rule and are now required to implement continuous fenceline monitoring for six high-priority air toxics:
- Chloroprene
- Benzene
- 1,3-Butadiene
- Ethylene Oxide (EtO)
- Vinyl Chloride
- Ethylene Dichloride
Key Deadline for Ethylene Oxide Monitoring
Per the 2024 HON amendments, affected facilities that manufacture, process or store EtO must begin fenceline monitoring for EtO by July 15, 2026. The default method specified by the EPA, known as Method 327, requires 24-hour samples to be collected every five days using SUMMA canisters. While this method provides a baseline measurement of whether concentrations exceed the action level of 0.2 µg/m³, it offers limited spatial or temporal insight.
Method 327, while a starting point, has its limitations. It answers a simple question: is the average concentration above the threshold? However, it does not identify where emissions are coming from, when they are occurring, or how to investigate the cause. This is where more advanced monitoring systems come into play.
Of note, on July 17, 2025, President Trump issued a two-year exemption from the 2024 HON amendments for 52 named facilities operated by 25 companies. This includes an exemption from mandatory fenceline monitoring for these facilities.
Going Beyond Compliance
For facilities that want to proactively manage emissions or conduct effective root cause investigations, Method 327 may not be enough. By installing more robust monitoring systems, facilities can gain greater control over their operations, providing real-time or high-frequency data, delivering location-specific insights, and supporting informed operational decisions.
Depending on the need, systems can be installed temporarily for diagnostic purposes or integrated permanently to support long-term compliance and performance.
How EDGE Can Help
EDGE Engineering & Science brings deep expertise in air quality and emissions measurement and is well-positioned to support facilities as they prepare for the upcoming EtO monitoring requirements. With our proven track record and extensive experience, you can be confident in our ability to guide you through this process.
Our team can assist with:
- Defining regulatory requirements specific to your site
- Evaluating alternatives to Method 327
- Designing custom measurement systems
- Procuring and installing equipment for temporary or long-term use
- Selecting and customizing data analysis software
- Obtaining EPA approval for alternative monitoring methods
EDGE’s experts and technology partners bring extensive experience with advanced air monitoring systems. Each solution is built to align with your facility’s unique operations and goals.
Plan Now to Stay Ahead
With the July 2026 deadline now less than a year away, this is the time for regulated facilities to evaluate their monitoring strategies and begin preparations. Starting early allows time for technology selection, deployment planning, and regulatory approvals.
Contact EDGE today for #furtherinsight on how we can support your ethylene oxide monitoring program and help your facility stay ahead of changing regulatory demands.