Simplifying HON MACT Compliance with Real-Time Environmental Monitoring

What is HON MACT?

The Hazardous Organic National Emission Standards for Hazardous Air Pollutants (HON MACT) is a regulatory framework established by the U.S. Environmental Protection Agency (EPA) under the Clean Air Act. It sets strict emissions control requirements for facilities that manufacture synthetic organic chemicals, polymers, and resins.

The updated HON MACT rule, which took effect on July 15, 2024, aims to reduce hazardous air pollutants (HAPs) that pose significant risks to public health and the environment. More than 200 U.S. facilities must comply with or commence enhanced fenceline monitoring, tighter emissions limits, and new reporting obligations by July 2026.

Key Compliance Changes in the Updated Rule:

Fenceline Monitoring Requirements – Facilities that use, produce, store, or emit any of six air toxics—ethylene oxide (EtO), benzene, 1,3-butadiene, chloroprene, ethylene dichloride, and vinyl chloride—must conduct ongoing fenceline monitoring by collecting and analyzing samples using Method 325A/B (passive adsorbent tubes) and/or Method 327 (canisters).

Stricter Emissions Limits – New thresholds target high-risk pollutants, particularly hazardous air pollutants.

Who Does HON MACT Apply To?

The HON MACT rule applies to facilities that manufacture, process, or store hazardous organic chemicals. The regulation primarily impacts the Synthetic Organic Chemical Manufacturing Industry (SOCMI) but also extends to Polymers and Resin Industries (P&R I and P&R II) and other operations handling hazardous air pollutants (HAPs).

Elimination of Exemptions – The rule removes startup, shutdown, and malfunction exemptions, requiring continuous compliance.
Enhanced Flare Efficiency Standards – Stricter controls on flares to reduce volatile organic compound (VOC) emissions.
Mandatory Root Cause Analysis – If emissions exceed limits, facilities must identify and address the cause within 30 days or switch to real-time monitoring.
Compliance and Emissions Data Reporting Interface (CEDRI)– Fenceline monitoring reports must be submitted on a quarterly basis using the appropriate electronic report template found on EPA’s CEDRI website.

Industries Affected

Chemical manufacturing plants producing synthetic organic chemicals
Pharmaceutical production facilities that use or emit regulated HAPs
Petrochemical refineries and processing plants
Operations involving distillation, reactors, and storage tanks emitting HAPs
Facilities handling benzene, toluene, xylene, and similar compounds

Why Compliance Matters

Facilities subject to HON MACT must implement strict emissions controls to meet EPA regulations. Non-compliance can result in fines, operational shutdowns, and reputational damage. Additionally, with increased public scrutiny and ESG (Environmental, Social, and Governance) expectations, businesses must demonstrate proactive environmental responsibility.

Companies must assess whether their current monitoring systems can keep up with these new demands or risk facing costly penalties.

Compliance Requirements

To comply with HON MACT, facilities must implement fenceline monitoring, emissions controls, and reporting practices to track and reduce hazardous air pollutants (HAPs). The updated rule introduces stricter standards that require continuous monitoring and faster response times when exceedances occur.

Key Compliance Requirements

1. Fenceline Monitoring & Emissions Testing

Facilities must perform ongoing air quality monitoring at facility boundaries using EPA Methods 325A/B and M327.
If pollutant levels exceed regulatory limits, a root cause analysis must be conducted within five days, with corrective action completed within 30 days.
If the issue isn’t resolved within that timeframe, facilities must implement real-time monitoring to track emissions continuously.

2. Stricter Emissions Limits

The rule sets lower emissions thresholds for key hazardous pollutants, including:

Ethylene Oxide (EtO) – A significant reduction to mitigate cancer risk.
Chloroprene – Tightened limits based on recent public health findings.
Volatile Organic Compounds (VOCs) – New flare efficiency standards to improve emission control.
Dioxins & Furans – Additional limits targeting highly toxic compounds.

3. Elimination of Startup, Shutdown, and Malfunction (SSM) Exemptions

The previous exemption allowing emissions during these events is now eliminated.
Facilities must have continuous compliance measures in place, even during operational disruptions.

4. Expanded Data Collection & Reporting

Companies must maintain detailed emissions records, exceedance events, and corrective actions.
CEDRI reports must be submitted to the EPA and made available to regulators for compliance verification.

The new compliance requirements demand more frequent monitoring, faster response times, and greater transparency. Many facilities will need to upgrade their monitoring technology and data management systems to meet these new standards effectively.

Challenges in Compliance

Meeting the updated HON MACT requirements presents significant challenges for facilities, especially those relying on traditional monitoring methods. The new rule demands continuous data collection, rapid response to exceedances, and stricter regulatory oversight, all of which can strain existing compliance processes.

Managing Large Volumes of Data

Facilities must aggregate emissions data from multiple sources, including fenceline monitors, internal air quality sensors, and lab testing results. Manual data processing is no longer sufficient—companies need automated systems to store, analyze, and act on emissions data in real-time.

Delayed Data from Traditional Monitoring

Standard fenceline monitoring methods, such as passive sampling (Method 325A/B), require samples to be collected over 14-day periods, leading to delayed detection of emissions exceedances.

If exceedances occur, facilities must conduct a root cause analysis within five days—a tight, difficult timeframe without access to real-time emissions data.

Increased Regulatory Burden

Compliance now requires detailed record-keeping, increased sampling, and stricter reporting.

Facilities must track and report emissions data continuously, which adds complexity to operations.

With no exemptions for startup, shutdown, or malfunctions, companies must maintain consistent compliance under all conditions.

Reputational Risk

Regulatory scrutiny is increasing, with the EPA and environmental advocacy groups closely monitoring compliance.

Facilities face pressure from investors, stakeholders, and the public to demonstrate environmental responsibility and maintain strong ESG (Environmental, Social, and Governance) performance.

Failure to comply could lead to financial penalties, legal action, and reputational damage.

How Real-time Air & Sensible EDP Make it Easy

With HON MACT’s stricter compliance requirements, facilities need a real-time, automated monitoring solution to efficiently track emissions, respond to exceedances, and simplify reporting. Sensible EDP provides a scalable, sensor-agnostic platform that enables companies to stay compliant while reducing operational burdens.

1. Real-Time Environmental Monitoring

Unlike traditional passive sampling methods, Sensible EDP enables real-time emissions tracking, allowing facilities to detect issues immediately rather than waiting weeks for lab results.
The platform integrates data from sensors, satellites, flyovers, OGI surveys, and other 3^rd party measurements, offering a comprehensive view of emissions data in one place.
If an exceedance occurs, Sensible EDP provides instant alerts, helping facilities efficiently meet the five-day root cause analysis deadline.

2. Automated Compliance & Reporting

Sensible EDP automates emissions data collection, analysis, and reporting, significantly reducing the time and effort required to meet regulatory requirements.
The system generates EPA-compliant reports and maintains a detailed audit trail, ensuring facilities are always prepared for inspections and regulatory reviews.

3. Seamless Integration with Existing Monitoring Systems

The platform is sensor-agnostic, meaning it can integrate with any existing air monitoring equipment a facility already has in place.
Sensible EDP works alongside EPA-approved fenceline monitoring methods (325A/B, 327) and real-time monitoring solutions—ensuring compliance with HON MACT without requiring a complete overhaul of current infrastructure.

4. Scalable & Future-Proof Compliance Solution

As regulations evolve, Sensible EDP’s scalable platform ensures that facilities can quickly adapt to new requirements without major operational disruptions.
The platform provides historical data tracking, predictive analytics, and continuous improvements to help companies optimize their environmental compliance strategies.

Sensible EDP simplifies HON MACT compliance and reduces the risk of fines, operational shutdowns, and reputational damage. With real-time monitoring, automated reporting, and seamless integration, facilities can focus on proactive compliance and sustainability goals rather than struggling with data management.

Take Control of HON MACT Compliance with Sensible EDP

The new HON MACT regulations demand faster response times, stricter emissions controls, and more comprehensive data management than ever before. Staying compliant requires real-time monitoring, automated reporting, and seamless data integration—all of which Sensible EDP delivers.

Why Choose Sensible EDP?

Real-Time Emissions Monitoring – Detect exceedances immediately, avoiding delays and compliance risks.
Automated Compliance Reporting – Reduce administrative burden with EPA-compliant reports and audit-ready data.
Seamless Sensor Integration – Works with existing monitoring systems, eliminating the need for costly infrastructure overhauls.
Scalable and Future-Proof – Adapts to new regulations and evolving compliance requirements.

Get Started Today

Ensure your facility meets HON MACT compliance deadlines with a proven, real-time monitoring solution.

Schedule a demo to see how Sensible EDP can streamline your compliance process.

Montrose’s Real-Time Air solutions transform air quality monitoring into a competitive advantage for energy and industrial companies. Our sensor-agnostic platform consolidates emissions data into a single, intuitive dashboard—giving you real-time visibility to enhance safety, optimize efficiency, and maintain compliance with confidence.

With automated alerts and expert-driven insights, we go beyond data collection to help you mitigate risks, prevent costly fines, and stay ahead of evolving regulations. Our unique combination of cutting-edge technology and deep industry expertise empowers your team to make informed decisions, reduce operational disruptions, and drive sustainable success.

Montrose doesn’t just provide monitoring—we deliver clarity, control, and peace of mind.