When it comes to air quality and emissions monitoring, real-time data isn’t a luxury—it’s a necessity. From mitigating risk in chemical plants to optimizing sterilization processes, rapid, accurate emissions insight is essential for compliance and operational efficiency. Successful ambient air monitoring requires the ability to discriminate target compounds down to single-digit ppb, even in the presence of high concentrations of interferences, such as water, carbon dioxide, and hydrocarbons.
Fourier transform infrared spectroscopy (FTIR) delivers on that need. FTIR gas analyzers provide high-sensitivity, multi-gas detection—including ultra-low levels of ethylene oxide (EtO), hazardous air pollutants (HAPs), and volatile organic compounds (VOCs)—with robust spectral resolution and stability, even in challenging matrices or high-humidity conditions. FTIR is recognized as a promulgated EPA methodology for emissions monitoring, backed by decades of use and battle tested. With FTIR, you meet all regulatory requirements, ensuring compliance and safety in a straightforward and reliable way.
Why FTIR?
FTIR is the preferred choice for industries using ethylene oxide (EtO), such as sterilization and chemical manufacturing, for accurate monitoring, compliance, and safety assurance. However, its utility extends well beyond EtO. FTIR is widely used across various heavily regulated sectors—including semiconductor, power generation, cement, hazardous waste combustion, and automative manufacturing—making it a trusted and proven technology for continuous HAP(s) & VOC(s) monitoring.
FTIR is recognized by regulators for its reliability and ease of use. It’s approved for compliance monitoring under several EPA standards, including:
- Hazardous Waste Combustors (40 CFR Part 63, Subpart EEE): For real-time measurement of HCl, HF, formaldehyde, and other HAPs under MACT standards.
- Portland Cement Plants (40 CFR Part 63, Subpart LLL): For monitoring HCl, formaldehyde, and acid gases.
- Boilers and Industrial Furnaces (BIFs, under RCRA): For multi-component monitoring, including HCl, HF, CO, and VOCs.
- Ethylene Oxide Monitoring (40 CFR Part 63, Subpart O & Performance Specification 19): FTIR is increasingly used for EtO compliance due to its sensitivity and real-time capability.
- Semiconductor Manufacturing (40 CFR Part 63, Subpart I): FTIR supports emissions monitoring of fluorinated compounds, acid gases, green house gases (GHGs), HAPs, and VOCs used in semiconductor processes.
- Turbine Applications (40 CFR Part 60, Subpart YYYY): FTIR is the gold standard for low-level formaldehyde & ammonia measurements.
- USEPA Methods:
- Method 320: A broad, generic FTIR method for continuous gas-phase measurements.
- Method 318: Applicable for fiberglass manufacturing facilities.
- Method 321: Designed for emissions testing at cement plants.
Benefits of FTIR
FTIR technology provides real-time detection and quantification of HAPs & VOCs, even at low concentrations, while simultaneously identifying other gases. Its high sensitivity and ability to manage complex emission streams make it particularly effective in environments with multiple HAPs & VOCs, high interferant concentrations (H2O, CO2, etc.), and processes with varying conditions. Continuous monitoring helps facilities respond quickly to process upsets, worker exposure, and potential emissions deviations thus reducing risks, optimizing performance, minimizing downtime, and enhancing workplace safety.
When paired with an advanced data platform like Montrose’s Sensible EDP, FTIR simplifies emissions tracking and compliance reporting. With Sensible EDP, you get automated alerts, centralized dashboards, and easy access to historical data—making compliance hassle-free. FTIR systems require minimal operator oversight, and routine system validation ensures consistent, defensible data for inspections and reporting.
FTIR has been used as a compliance and engineering tool for decades. Here’s why FTIR is an ideal choice for real-time emissions monitoring:
FTIR Provides Continuous, Real-Time Monitoring
FTIR analyzers offer non-stop detection and quantification of HAPs & VOCs, making them ideal for regulatory compliance, engineering studies, and process optimization. Continuous monitoring helps users immediately identify deviations, manage emissions, and reduce the risk of non-compliance or safety incidents.
High Sensitivity and Multi-Gas Capability
FTIR can simultaneously detect multiple gas species, including low parts-per-billion (ppb) concentrations of EtO. This makes it a cost-effective and efficient option for facilities that need to monitor EtO along with other HAPs or VOCs.
Ideal for Complex Emission Sources
HAPs & VOCs commonly need to be monitored in environments with complex gas streams. FTIR’s ability to handle interfering compounds and deliver reliable speciation data ensures accurate readings, even when other chemicals are present.
Regulatory Acceptance
FTIR is widely regarded as the premium standard for industrial emissions monitoring and is routinely used by gas vendors to certify calibration gases. It’s an EPA-approved methodology for monitoring numerous HAP & VOC emissions, meeting EPA, State, and even site–level standards. FTIR provides verifiable, auditable data that supports compliance during inspections and regulatory reporting —making it the method of choice for some of the most high-profile emissions studies conducted globally. Some of the most high-profile emissions studies performed in the world have been done via FTIR.
Seamless Integration with Data Platforms
Modern FTIR systems integrate with platforms like Sensible EDP to provide:
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NESHAP & FIFRA-specific centralized dashboards
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Real-time alerts (email/SMS)
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Historical data analysis
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Automated compliance reporting via CEDRI (when available)
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Streamlined data management
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Enhanced decision-making.
Calibration and Maintenance Matter
Accurate emissions monitoring with FTIR requires routine calibration and validation to ensure data accuracy and regulatory defensibility. Users should work with providers that offer ongoing support, automated quality assurance, and routine maintenance. While FTIR is a powerful tool, it’s important to remember that all emissions monitoring systems require careful setup, validation, and upkeep. There’s no “easy button” in emissions monitoring; no system is perfect. Success depends on pairing the right technology with expert support and a strong QA/QC program.
Enhanced Safety and Risk Mitigation
Real-time FTIR monitoring helps detect EtO, other HAPs, and VOCs concentrations early, reducing health risks to workers and nearby communities. By flagging exceedances immediately, facilities can take corrective action before safety or compliance issues escalate.
Field Proven Solutions for Continuous Emissions Monitoring Systems (CEMS)
Montrose Environmental offers top-of-the-line FTIR CEMS for Ethylene Oxide (EtO), supporting compliance with federal and state regulations such as NESHAP, Rule 1409, and FIFRA. Utilizing EPA Method 320, our systems deliver high-quality, real-time data for EtO and a wide range of other hazardous air pollutants (HAPs). With flexible configurations like EMS-10, iAQ, and Temp FTIR CEMS, we provide our clients with reliable, field-proven solutions for both permanent and temporary monitoring needs. Our Temp CEMS setups are frequently deployed to support short-term compliance, engineering studies, or research projects—delivering continuous emissions data during pilot-scale process changes, control technology evaluations, or while facilities await permanent CEMS installation.
A Smarter Approach to Emissions Management: Comprehensive Monitoring with Thermo Fisher & Sensible EDP
Measuring challenging compounds like ethylene oxide, acid gases, fluorinated compounds, and combustion analytes requires advanced technology. This technology must avoid false readings and comply with standards set by regulatory bodies such as the Environmental Protection Agency (EPA) and the US Occupational Safety and Health Administration (OSHA).
In collaboration with Thermo Fisher Scientific, Montrose Environmental Group has developed an integrated solution to help industries tackle emissions compliance and real-time monitoring challenges. By combining Montrose’s project services expertise, the Sensible Environmental Data Platform (EDP), and Thermo Fisher’s StarBoost™ Optically Enhanced MAX-iAQ™ OE-FTIR Gas Analyzer and EMS-10 Continuous Emissions Monitoring System, organizations gain access to a high-performance emissions tracking system.
The MAX-iAQ OE-FTIR Analyzer delivers high-sensitivity, low-level detection of ethylene oxide and other target compounds, even in hot, humid, and challenging matrices to monitor worker exposure. Paired with the EMS-10 CEMS, which automates sampling, QA procedures, and real-time reporting, the system offers a reliable, low-maintenance solution for continuous compliance monitoring. Together, they provide precise emissions data with minimal operator oversight.
Sensible EDP enhances this solution by serving as the central hub for real-time data visualization, alerts, and historical trend analysis. Its seamless integration with FTIR systems ensures that emissions data is not only collected accurately, but also immediately actionable—supporting rapid response, streamlined reporting, and smarter environmental decision-making across facilities.
Need help implementing FTIR for HAPs monitoring? Explore the unique advantages and innovations—like the MAX-iAQ and EMS-10—that make FTIR a smart, reliable choice for continuous compliance monitoring.
About the Authors
Sean Wheeler
Operations Manager, SMS
Sean is a results-driven Project Manager with over a decade of experience leading regulatory-compliant projects, specializing in ethylene oxide monitoring, data-driven decision-making, risk management, and stakeholder communication to ensure high-quality outcomes.
Blake Ericson
Business Development Manager
Blake has nearly a decade of experience in air quality, engineering, and regulatory testing—specializing in FTIR technologies—who also brings a strong background in financial forecasting, client growth strategy, and performance analysis to support business expansion and customer retention.
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