DEPARTMENTS
VIEWPOINT
SPENCER PIZZANI, CIH, is the occupational health manager for PepsiCo Global EHS.
The opinions expressed in this article are the author’s and do not necessarily reflect those of AIHA® or The Synergist®.
Send feedback to The Synergist.
Ten Compelling Uses for FTIR in Industrial Hygiene
BY SPENCER PIZZANI
Disclaimer: This article is not a substitution for evaluation by a professionally competent industrial hygienist. It represents the opinions of the author only.
Fourier-transform infrared (FTIR) spectroscopy uses an interferometer to obtain the absorption spectra of any whole gas sample. By analyzing the behavior of an infrared source, instrumentation can identify many chemicals by the characteristics of known spectra. Simply put, FTIR matches sample spectra to a library and determines which spectra match best to determine what, and how much, of a chemical is present in the analytical cell. Portable FTIR devices now allow this analysis in the field, providing new capabilities for use in industrial hygiene applications, several of which are discussed below.
1. COMPLETE CHARACTERIZATION OF CONFINED SPACES
While “four-gas” meters are commonly associated with confined space entry, regulations and good industrial hygiene practice require a complete characterization to determine the presence of toxins. Overlooked atmospheric hazards have killed entrants, including when the agent is a product of chemical processing or byproducts of secondary chemical changes.
FTIR allows for broad-scope detection of potentially hazardous agents that may not have been qualitatively identified in a job hazard analysis or confined space characterization event. This capability is especially important if these agents are present as byproducts of combustion, unexpected or unidentified leaks, or when the potential agents present have poor warning properties, such as being odorless.
2. IDENTIFY AGENTS THAT HAVE NO ALTERNATIVE METHODS
Perhaps the most compelling use of FTIR in industrial hygiene is when no agent-specific methods exist. This is the case for dimethyl dicarbonate and other agents that have challenging chemistry but clear spectra.
When the alternative to exposure assessment includes complex deterministic models or results in supplied air from respirator decision logic, the use of FTIR is especially compelling. Even if a specific compound cannot be quantified below the occupational exposure limit, FTIR can often eliminate the need to use supplied air when the atmosphere cannot reasonably be determined to be below the immediately dangerous to life or health (IDLH) value.
3. COMPARE SPECTRA, WHICH NEVER DEGRADES
A major advantage of FTIR is the ability to capture spectra that can be analyzed later in novel ways. Mass-capture methods rely on sample preservation and can introduce error from analyst technique. In contrast, spectra can be analyzed over and over again. This is especially important for investigations where new information comes to light later: comparison of spectra can eliminate potential contributions from other substances or allow hypothesis testing and model falsification.
4. LIMIT OR ELIMINATE THE EFFECTS OF INTERFERENCES
Many chemicals have interferences that may limit the effectiveness of less complex sensors. For example, hydrogen is often detected as carbon monoxide, oxides of nitrogen and sulfur often cannot be simultaneously evaluated, and radio interference can display as agent concentration on newer Bluetooth-equipped personal monitoring devices.
FTIR can eliminate interferences that would otherwise exist in sensors. This advantage extends to laboratory extraction processes for concentration methods, which may be highly selective for target analytes. For example, evacuated-canister whole-gas samples may need special preparation to be analyzed for hydrogen and volatile organics simultaneously.
5. PINPOINT THE RIGHT MOMENT FOR FURTHER ANALYSIS
Transient detection of contaminants is a perennial problem in hazard evaluation. Contaminants may only be present for a brief time. When the opportunity cost of whole-gas capture is high, FTIR may be the only technology fit for purpose for analysis. Similarly, many concentration methods require time, as dictated by volume, for sufficient collection to be quantified in a laboratory. Use of FTIR can allow for analysis of complex mixtures where no other method is feasible.
FTIR allows for broad-scope detection of potentially hazardous agents that may not have been qualitatively identified in a job hazard analysis or confined space characterization event.
6. IDENTIFY SPECIFIC AGENTS FOR MORE DETAILED ANALYSIS
FTIR is extremely useful in determining which agents are present among many possible candidates, especially when similar chemicals have very different absorbance spectra. Examples include evaluation of chemicals that rapidly oxidize in air, those that degrade rapidly, those that have similar odors, or those where odor appears only in the presence of moisture or extended contact with light. These may include peroxides, oxides of nitrogen, or compounds with cyanic acids.
Identifying specific agents of concern can allow for targeted monitoring or further analysis with more sensitive instrumentation or more finely tuned methods.
7. IDENTIFY SOURCES OF ODORS AND POTENTIAL HAZARDS
Odor investigation may be simplified by identification of spectra associated with the complaint. This is especially true when attempting to determine if an odor is fundamentally biological in origin or a result of chemical off-gassing. For example, FTIR may be used to determine if a fishy odor is microbial growth; associated with amines off-gassing from sprayed polyurethane foam insulation; or the result of water infiltrating urea-formaldehyde foam insulation, causing an ammonia odor that resembles animal urine.
Eliminating possibilities quickly with real-time detection may simplify the process of determining which control and abatement actions to take. While many odor thresholds are below the limits of identification or quantification for any technology, identification may simplify the investigation.
8. IDENTIFY CONTAINER CONTENTS
Inadequate or degraded labeling or deficient chemical handling techniques may frustrate our attempts to understand the contents of containers. Additionally, identifying the contents of orphan containers may be the objective of our field investigation. FTIR offers the capability to potentially identify the contents of such containers, allowing for immediate response actions and the narrowing of investigations. It may also help direct efforts on waste characterization, identification of incompatible materials, or incident investigation.
9. CONFIRM QUALITY AND SAFETY
With a global supply chain, ensuring the quality and veracity of safety information is challenging. FTIR may allow an IH to confirm the absence of a chemical above a limit of identification—for example, that a specific paint is free from benzene solvent or a specific shipping container does not contain phosphine fumigant. Such sampling can simplify supply-chain quality control and may eliminate the need for prophylactic respiratory protection, such as when no other immediate methods of measurement exist.
10. LIMIT THE SHORTCOMINGS OF MORE TRADITIONAL METHODS
There are numerous shortcomings associated with agent-specific methods, such as the difficulty of avoiding size bias in isocyanate sampling, challenges with limited media shelf-life and frozen analytical media for ozone, or determining specific terpenes from among natural sources.
Collection of integrated (“pump and tube”) industrial hygiene samples is also subject to other sources of error, including sample degradation, analyte extraction and recovery in a laboratory, and degradation in transit due to light, temperature, or chemical changes. Even with modern overnight shipping, chemical extraction may not occur until 18 hours after shipping.
Use of FTIR allows for initial results within minutes for agents or whole atmospheres that cannot be reasonably stabilized for remote analysis. FTIR can also help establish higher resolution data, characterize momentary exposure ceilings, and discriminate among multiple potential agents in a way no other direct-reading instrument can.
RESOURCES
AIHA: “Overview of Isocyanate Air Sampling and Analysis Methods,” AIHce 2015 (presentation by K. Mattson, May 2015).
Environmental Monitoring and Assessment: “A Method Development for Bacterial Quantification and Qualification in Occupational Exposure” (January 2020).
Journal of the Air & Waste Management Association: “Applications of Open-Path Fourier Transform Infrared for Identification of Volatile Organic Compound Pollution Sources and Characterization of Source Emission Behaviors” (June 2008).
Journal of Occupational and Environmental Hygiene: “Methemoglobinemia Resulting from Exposure in a Confined Space: Exothermic Self-Polymerization of 4,4'-methylene Diphenyl Diisocyanate (MDI) Material” (January 2017).
Journal of Occupational and Environmental Hygiene: “Rapid Method for Determining Dermal Exposures to Pesticides by Use of Tape Stripping and FTIR Spectroscopy: A Pilot Study” (December 2007).
Navy and Marine Corps Public Health Center: “Industrial Hygiene Sampling Guide for Comprehensive Industrial Hygiene Laboratories (CIHLs)” (PDF, December 2021).
Uppsala University: “Fourier Transform Infrared Spectroscopy in Industrial Hygiene Applications: Assessment of Emissions from and Exposures in Wood Processing Industries” (PDF, 2004).