Concerns about exposure to trace toxins and the effects of that exposure on workers and the general population are growing globally, with many countries passing new regulations intended to limit the impact on long-term health risks such as cancer and birth defects. In the United States, trace air toxins—also known as hazardous air pollutants (HAPs)—are regulated by the US Environmental Protection Association (EPA) through the Clean Air Act. The act identifies 187 substances such as benzene, trichloroethylene, formaldehyde, mercury, and chromium as HAPs. Major sources of these hazardous air pollutants include emissions from chemical plants, petroleum refineries, and power plants. The need for HAPs control also exists wherever toxic compounds are commonly used, such as in semiconductor fabrication, medical equipment sterilization, or in pharmaceutical facilities.

Generally, airborne HAP emissions are measured in the form of source emissions directly at the output stack, or via ambient air monitoring in and around the worker environment or at the fence line of the facility. Both methods rely on continuous emission monitoring (CEM) to ensure the cumulative exposure is measured over time. While similar, the requirements of source emission monitoring and ambient air monitoring can be very different in both minimum detection limits and measurement conditions. Thus, the need exists for specialized systems to address the demands of each. 

Employees of facilities where HAPs are used can have a higher risk of exposure than the surrounding community due to source proximity. This is understandable since levels of HAPs can accumulate more quickly in confined spaces if abatement systems are not working at optimum efficiency. While laws exist to protect the health and safety of workers, managing indoor air quality continues to be a major concern and therefore requires a robust solution. 

There are several challenges associated with monitoring for trace toxins in ambient air: 

  1. The analytical technology used for monitoring must be capable of measuring many different HAPs that can be present in the same area.
  2. The detection limits must be low enough to measure compounds at levels below the permissible exposure limit (PEL), with concentrations typically in parts-per-million (ppm), parts-per-billion (ppb) or even parts-per-trillion (ppt), depending on the compound.
  3. The technology must not be affected by cross interferences from other compounds or naturally occurring atmospheric gases (CO2, H2O, CH4) that dominate ambient air at ranges from ppm to percent and often obscure the detection of trace HAPs.
  4. Fast measurement speed is required such that multiple input locations can be measured in a timely fashion. This reduces the risk of missing transient trace emissions which are common in ambient air conditions, and it minimizes workers’ exposure time to such emissions.

The traditional technologies for measuring HAPs have been gas chromatography (GC) and Fourier transform infrared spectroscopy (FTIR). Both technologies have their pluses and minuses, with FTIR being a significantly better option for simultaneous measurement of multiple compounds, resilience to cross interferences, and speed. GCs, on the other hand, are superior in terms of sensitivity yet are slower and more costly to operate in a factory environment. 

A new technology called optically enhanced FTIR (OE-FTIR) has been introduced for industrial gas analysis. OE-FTIR provides all the traditional benefits of FTIR as well as a significant increase in sensitivity for HAP detection that not only meets the capability of GCs but also exceeds them in many cases. Even newer laser-based technologies such as cavity ring down systems (CRDS) have a difficult time competing with OE-FTIR, as the CRDS signal tends to degrade over time when exposed to air particulates such as dust. In addition, CDRS systems are only capable of measuring one compound per laser; this rapidly becomes cost prohibitive when measuring for multiple compounds. 

While no technology is perfect, OE-FTIR has changed the paradigm in obtaining fast and robust HAP measurements down to the lowest levels needed to ensure worker safety. The result is a sensor technology that, when integrated into a well-designed CEM system, provides environmental health and safety managers with the ability to increase worker protection without incurring higher operational costs. 

OE-FTIR enables the following benefits when integrated into a properly designed CEM:

  • Wide area monitoring can be configured for up to 20 sample points and still provide rapid full-cycle time.
  • As an optical technology, the OE-FTIR system software can be fully automated to run the analyzer without human intervention and without the need for calibration.
  • Realtime control room monitoring allows for rapid response to emission events.
  • There is no need for carrier gasses and expensive data interpretation when interferents are present, thus reducing the cost of ownership. 

The revolutionary new OE-FTIR technology is commercially available in the Thermo Scientific™ MAX-iR™ FTIR Gas Analyzer and Thermo Scientific™ MAX-iAQ™ Ambient Air Monitoring System.

For more information on this new industrial gas technology, visit