From accidental leaks and improper handling of hazardous materials, to an intentional chemical attack, exposure to unknown or toxic chemicals can happen anywhere. Due to the rising threat of terrorism and the myriad ways people can be exposed to toxic materials in the environment, the ability to detect and identify chemical threats is more crucial than ever.
A critical line of defence is the combination of chemical threat detection tools and the personnel who operate them. But before selecting equipment in the responder toolkit, it’s first important to understand the landscape of chemical hazards and their potential impact on life, property, and the environment:
- Health Hazards: narcotics, chemical warfare agents and toxins.
- Physical Hazards: Flammable chemicals, corrosive/oxidising agents, and explosives.
- Environment Hazards: Toxic industrial chemicals.
Operators must also understand the state of the hazard (vapour, liquid, or solid) for critical on-scene response. This can inform the operator about what kind of personal protective equipment (PPE) is required, along with sample or evidence collection procedures and the selection of proper detectors.
Trace Versus Bulk Sampling
Another important consideration is the quantity of a threat that needs to be sampled: bulk or trace.
In practice, a bulk sample can be seen and easily weighed, while a trace sample is virtually invisible. Concealed threats typically have trace residue on the exterior; therefore, a detector with trace-level sensitivity is required. Further, many gas-phase threats can cause harm at the trace-level, so having a system that can detect minute amounts is critical.
Conversely, solid threats are typically considered bulk. Although most trace detectors can detect bulk samples, operators can expect a trade-off on system performance.
Types of Chemical Response Tools
By understanding the various types of chemical threats, the phases of matter and differences in sample quantities, operators can then consider what chemical response tools are required. After all, no single tool will accomplish every task. Chemical detectors vary in sensitivity and specificity, so it’s important to understand the capabilities of each technology to select the right tools for the job.
Detection/Classification Tools (Least Costly)
- Colourimetric: Single-use, inexpensive tests to determine the presence of a threat and its chemical class.
- Multi-Gas Monitor: Used to detect toxic gas leaks, including carbon monoxide and chlorine. Some monitors are equipped with photo-ionisation detectors for volatile organic chemical (VOC) detection, but they are susceptible to interferants and are not confirmatory.
Presumptive Identification (Middle Cost Range)
- Spectroscopic Tools, including Raman and Fourier-Transform Infrared (FTIR) Spectroscopy: Primarily used for bulk samples, these can quickly interrogate unknown solids and some liquids, including narcotics and explosives. This equipment is lightweight and fast, but not ideal for trace-level detection or complex mixtures.
- IMS (Ion Mobility Spectrometry) Systems: Quick and sensitive, IMS systems provide critical early warnings of chemical threats but are prone to frequent false positive readings due to sample overloading and environmental effects.
- High-Pressure Mass Spectrometry (HPMS): An emerging technology, this tool only uses mass spectrometry for analysis. It has similar benefits and drawbacks to IMS, but enables larger libraries and greater data processing along with fewer false alarms.
Confirmatory Identification (Most Costly)
- Portable or lab-based Gas Chromatography–Mass Spectrometry (GC-MS): A gold standard technology, GC-MS tools analyse complex samples, including vapour, liquid, and solid-phase chemicals. Although the most expensive, GC-MS is selective and sensitive while offering the broadest capability, making it the ultimate confirmatory tool.
Consider Chemical Libraries
Chemical libraries are the software, electronic, or colour change-based templates for the responses of certain chemicals. Libraries range in fidelity from a colour shift on pH paper to electronically matching the mass fragment chemical fingerprint.
When determining the appropriate tools, review the missions and types of threats encountered. Some operators may consistently respond to the same 10-15 threats, suggesting a colourimetric tool might work best. For others, the ability to identify unknown chemicals is mission critical.
Ease-of-Use And Survivability
In addition to detection capabilities, it’s just as important to consider the specific conditions and scenarios in which a given tool and its personnel may be placed. Hazardous environments demand tools that are not only easy to use, especially when individuals must operate quickly while wearing PPE, but can also survive extreme conditions.
Determining the Toolkit
With all the factors listed above, governments and organisations responsible for chemical detection must also consider costs, the required coverage area and personnel training. Only then can they take the appropriate steps required to create a truly effective chemical detection toolkit.
In the end, the right toolkit can be the difference between a catastrophe and a rapid response that helps keep the public and personnel safe from harm.
Clint Wichert M.S., Director of Product Management, FLIR Detection