Multiple technologies are needed to measure all gases in all concentrations in all CBRNE scenarios. The right technology depends on the task and the measurement conditions.

Why no single technology can solve every CBRNE measurement challenge

In CBRNE monitoring and analysis, gas measurement needs vary greatly. In CBRNE research, laboratory research and field research may have different needs. Field research can be used to simulate the effect of environmental conditions and to practice response, while laboratory research can dive deeper into the chemistry of compounds of interest.

In CBRNE field measurements, there is a need for both: rapid field detection and in-depth field analysis.

These scenarios may come with different sampling setups and sample volumes, ranging from manual gas sampling of a few milliliters to area monitoring of large indoor spaces or outdoors. The measurements may produce either continuous or non-continuous results.

The concentration levels of compounds of interest can range from ppb levels to volume percent levels. Required detection limits and concentration ranges vary greatly. For chemical warfare agents (CWAs), lethal concentrations may be extremely low, whereas relevant concentrations and concentration changes for combustion gases may be relatively high.

Compounds of interest also vary greatly, ranging from CWAs, their precursors and reaction products to toxic industrial chemicals (TICs) and combustion gases.

In general, multiple technologies are needed to measure all gases in all concentrations in all scenarios. How, then, do you determine which technology is right for each scenario? Let’s dive in.

CBRNE field detection – quick and small

CBRNE field measurements may start with initial field detection in seconds. Field verification and analysis can then confirm the initial detection, survey the area, and help find the source.

Initial field detection

Priorities in field detection include response time, portability, and ease of use. Detection limits should ensure that hazardous concentrations are detected, typically at individual ppm levels or even below 1 ppm.

One of the technologies typically used for field detection of hazardous gases is ion mobility spectrometry (IMS). IMS provides maximum portability, making it highly field deployable. It has a rapid response within seconds, and continuous results allow changing concentrations to be followed. However, IMS is limited in selectivity, as the number of gases measured simultaneously is typically small. There can also be cross-sensitivities. All in all, IMS is an excellent choice when instantaneous initial field detection is needed.

Field verification and analysis

Another technology is needed to verify the results if something is suspected of being present, and that is Fourier transform infrared spectroscopy (FTIR) analysis. Portable FTIR analyzers are less portable than IMS detectors, and the response time is typically around one minute. Nevertheless, FTIR provides excellent selectivity, enabling qualitative measurements of more than 5,000 gases. Detection limits are most often in the sub-ppm range and typically below relevant exposure limit values.

FTIR is not limited to preconfigured gas lists, so identification of unknown compounds is also possible.

In the field, a portable FTIR analyzer should be the method of choice for spatial concentration mapping, source identification, all-clear confirmation, or quickly identifying unknown compounds.

Laboratory verification of field samples

In cases where, for example CWA use is suspected, the field analysis and detection may need laboratory verification. Manual samples are then taken from the field and analyzed in the laboratory by using gas chromatography-mass spectrometry (GC-MS).

Portable GC-MS systems also exist, but their deployability outside the laboratory is often constrained by their size, operational complexity, and the need for a carrier gas bottle. Even though its field applicability is limited, GC-MS may also be useful in mobile laboratory settings when small sample volumes are expected.

The ideal combination for the field

The ideal combination for the field is a simple, robust detector such as IMS that allows rapid detection of key compounds in seconds, complemented by thorough field analysis with FTIR.

IMS provides rapid initial detection, while FTIR adds the selectivity and flexibility needed for verification, identification, and situational awareness.

FTIR allows verification of the gaseous compounds present, source identification, and all-clear confirmation for the area in question. When additional confirmation is required, field samples can be verified independently in the (mobile) laboratory using GC-MS.

CBRNE laboratory analysis – high-quality results

Priorities in CBRNE laboratory research are typically sensitivity and selectivity or result quality, as well as the ability to measure as many components as possible.

Gas chromatography-mass spectrometry: maximum sensitivity for laboratory analysis

Gas chromatography-mass spectrometry (GC-MS) is a typical laboratory method. It is extremely selective and very sensitive. GC-MS can also handle small sample volumes, so it is suitable for analysis of manual samples from the field and laboratory alike. However, the response is typically slow, as it takes minutes to analyze one sample. The results are discontinuous, so GC-MS is not suitable for following rapid concentration changes in real time. Operating costs are typically high because of the need for a carrier gas and extensive or complicated maintenance.

GC-MS is the choice when the highest sensitivity is needed and the samples are not time-critical, or when sample volumes are very small.

FTIR in the labotory: real-time monitoring and flexibility

FTIR analyzers have strengths in the laboratory as well. FTIR gives a fast response and allows a real-time view of gas concentrations and their changes. It is well suited for following chemical reactions, identifying unknown compounds, and setups that require flexibility, such as transporting the measurement device, fitting it into small spaces, or changing the sampling setup. It is also a cost-efficient alternative to GC-MS and is often considered less complicated.

GC-MS provides maximum sensitivity in laboratory, while FTIR adds the real-time insight needed to understand how concentrations change.

FTIR is the choice for the CBRNE laboratory when you want to monitor concentration changes over time, need a quick, easy and cost-efficient way to do routine analysis, or want to compare laboratory and field measurements and bridge the gap between them.

Choosing the winning combo: how to select CBRNE gas measurement technology

There is no single solution that covers the multitude of needs in CBRNE-related gas analysis. Normally, a combination of methods is needed.

To select the right methods for your needs, at least the following should be considered:

• sensitivity and detection limits
• needed response time
• fit and form
• sampling considerations, including continuous or non-continuous measurements
• number of gases to be measured
• ability to identify unknown compounds
• cost balance

Good equipment will be your sidekick for years, even decades, so it is wise to think about possible future directions and requirements as well.

Good equipment is flexible equipment: it adapts to different usage scenarios and new compounds.

The goal is not to find the perfect measurement technology. The goal is to combine the right technologies for the task at hand.

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