Emergencies involving Hazardous Materials (HAZMAT) and Chemical, Biological, Radiological, Nuclear and Explosive (CBRNE) substances are some of the most dangerous situations faced by emergency first responders. Between 1980-81 and 2015-16, the number of reported HAZMAT related emergencies responded to by the fire and rescue services of Great Britain increased by approximately 67%. These types of emergencies involve solids, liquids, or gases which can harm people, other living organisms, property, or the environment.
When emergency responders are mobilized to the scene of a HAZMAT incident they can face any number of chemical, physical or biological hazards. Also, supposing that the information which has been conveyed to them during mobilization is incorrect or incomplete, the magnitude of the risk they face may be significantly increased! Therefore, it is imperative that first responders have access to the best Personal Protective Equipment (PPE), detection equipment, scientific backing and knowledge to protect themselves and the public.
Over the past several years, much research and development has been carried out in the HAZMAT sector. Primarily, this is so that first responders can have the best chance of tackling on-scene hazards whilst maintaining their own safety.
Let’s consider a ‘worst-case’ scenario: the potential release of a chemical warfare agent (CWA) like Sarin, Soman or VX (Fig. 1) in a densely populated urban area. On arrival at the scene first responders will wish to confirm or deny the presence of a CWA, as well as treat and evacuate any casualties within the inner cordon. But before doing so, they must first don sufficient PPE so that they themselves don’t become affected by the hazards on-scene.
Typically, given the nature of this type of event, anyone entering the contaminated area will be required to carry their own clean air supply in the form of Self-Contained Breathing Apparatus (SCBA) and must wear a totally encapsulating chemical protective suit (Fig. 2).
Chemical protective suits are normally manufactured from high performance textiles, for example, p-aramid (poly-para-phenylene terephthalamide) and PBO (p-phenylene-2,6-benzobisoxazole) (Fig. 3). Both p-aramid and PBO can be produced using well defined chemical syntheses (Scheme 1), thereby allowing these suits to be manufactured with reasonable ease and at a relatively low cost.
p-Aramid and PBO are examples of polymers. Polymers are molecules which are composed of smaller repeating monomer units chemically bound together to form a long chain. As with all polymers, the properties which they display are primarily influenced by their chemical and physical structures. p-Aramid shows excellent thermal stability, ascribed to the presence of the aromatic ring within its structure and the high splitting energies of the amide (-NH-C(O)-) bonds. The latter of which have ‘double bond character’, which means that although the Nitrogen and Carbon atoms are formally only singly bound, the strength of the bond is somewhere between that of a single- and double-bond.
The aromatic rings of adjacent polymer chains can neatly stack atop each other. This increases the order and crystallinity (long-range ordering) of the polymer. The resulting physical outcome of this is the p-aramid fibers also have exceptionally good strength and mechanical stability.
So, after safely entering the contaminated area, responders must deduce what hazards are present. Nowadays, this is done via a selection of portable spectroscopic meters – though field test kits still do exist. In a laboratory setting, there are many empirical techniques and, more importantly, spectroscopic techniques which allow scientists to identify substances. The good thing about this is the accuracy and selectivity which is obtained from the lab-based tests are unrivalled. However, analysis can be slow, tedious, require significant chemical knowledge and cannot be carried out at the scene of an incident.
When at the scene of a HAZMAT incident it is imperative that the necessary resources can be accessed both easily and rapidly. This has led to the development of handheld identifiers, which can be easily transported by specialist response units and easily carried on one’s person to be used at the scene. These handheld devices use either Fourier Transform Infrared (FTIR) Spectroscopy or Raman Spectroscopy to quickly identify unknown substances.
FTIR spectroscopy relies on the internal vibrations of molecules to successfully identify the substance being probed. Chemical functional groups (carbonyl, hydroxyl, carboxylic acid, etc.) within a given substance each have characteristic vibrational frequencies, which can be easily linked to IR absorption bands in the recorded IR spectrum. This in turn can be analysed manually or automatically via a suitable database resource.
To make the idea of molecular vibrations easier to conceptualise, the analogy of a mass on a spring (Fig. 4) is frequently used to help describe functional group vibrations. If you imagine the mass on the spring being an atom (or group of atoms) and the spring being a chemical bond, when the spring is stretched and released it will begin to vibrate. Of course, the speed at which and duration of the vibration will depend on the rigidity (strength) of the spring and the size of the mass attached to it. This is the same concept used in FTIR for chemical analysis, except we are considering the mass of the atom(s) and the strength of the chemical bond!
Raman spectroscopy also operates via the vibrational excitation of a given sample. Monochromatic (single wavelength) light is fired at the sample and some of the light which is reflected from the surface is observed to be shifted in frequency. This implies that the some of the incident light has hit the sample surface and either lost or gained some energy. By measuring these differences in frequency (energy), it is possible to identify the sample by once again accessing a database resource.
Typically, the handheld Raman devices in common usage by HAZMAT teams have an incorporated 785 nm laser which is used to interrogate the sample. The downfall of this technology quickly becomes evident when attempting to identify a sample which is coloured or impure. Fluorescence interference hinders the recording of the Raman spectrum, which can ultimately lead to the sample not being successfully identified. As far as everyone on-scene is concerned, this is not a positive outcome, especially given the potential gravity of the situation.
However, the latest generation devices have begun using a 1064 nm laser which significantly enhances the capability of the unit. The higher frequency laser shifts the recorded Raman spectrum away from the area of interference, thereby allowing for, not only the analysis of coloured or impure substances, but also for the analysis of substances through the walls of a coloured or colourless container. The latter of which is very attractive to everyone at a HAZMAT scene since the material under investigation can remain sealed and contained.
There is always the possibility that the unknown substance may not be positively identified at the scene. If this were to happen, there would be few other options other than to send a sample for laboratory analysis. Though it is likely that several analytical techniques would be used in conjunction with one another, there is one technique which is particularly good at analysing CWAs – Ion Mobility Spectroscopy (IMS).
Ion mobility spectrometers are types of ionisation detectors. In other words, they’re able to identify ions (electrically charged species) as they move through a gaseous environment. Unlike other types of ionisation detector (e.g. flame induction detectors, electron capture detectors) IMS detectors can selectively distinguish between different components of a given sample. Analysis is carried out in a two-step process:
- Particulates of the unknown substance are ionised (charged) and molecules/fragments thereof are formed.
- The newly formed ions are separated and passed into the collector, built within the IMS detector. Here an output signal is generated which is then computationally processed and analysed by the IMS operator.
Therefore, due to the selectivity and analytical power of these techniques, it is possible for suspected CWAs to be successfully identified. With the continuous advancement of these technologies we can potentially make them more available and affordable. An analogous situation is found with the continuous development of PPE, protocols, sorption materials, surfactants, extinguishing media, and the list goes on. As a direct consequence, we will be able to further ensure the safety of all persons at a HAZMAT scene, and arm first responders with more powerful scientific tools to enable them to do their jobs more effectively and safely than ever before.
G. Smalldridge, Fire Statistics England : April 2015 to March 2016, 2017. Fire and rescue incident statistics Scotland 2015-16, 2016.
A. D. Maclean, J. Hazard. Mater., 1981, 5, 3–40.
In Department for Communities & Local Government and Chief Fire & Rescue Adviser – Fire and Rescue Authority – Operational Guidance – Incidents involving hazardous materials, 2012.
M. G. Holland and D. Cawthon, Emerg. Med. Clin. North Am., 2015, 33, 51–68.
R. Shishoo, Int. J. Cloth. Sci. Technol., 2002, 14, 201–215.
A. Knijnenberg, J. Bos and T. J. Dingemans, Polymer (Guildf)., 2010, 51, 1887–1897.
G. A. Holmes, K. Rice and C. R. Snyder, J. Mater. Sci., 2006, 41, 4105–4116.
N. Mao, High performance textiles for protective clothing, Woodhead Publishing Limited, 2014.
A. H. Plamboeck, S. Stöven, R. Duarte Davidson, E. M. Fykse, M. Griffiths, M. Nieuwenhuizen, C. Rivier and M. van der Schans, TrAC – Trends Anal. Chem., 2016, 85, 2–9.
C. Berthomieu and R. Hienerwadel, Photosynth. Res., 2009, 101, 157–170.
P. Larkin, Infrared Raman Spectrosc., 2011, 1–5.
B. Salvesen and M. Monaco, THMG080A – A talk with Rigaku – Nancy Otto, https://www.thehazmatguys.com/thmg080a, (accessed 19 May 2017).
J. Puton and J. Namiesnik, TrAC – Trends Anal. Chem., 2016, 85, 10–20.
Author: Steven Welsh
Steven is a final-year MChem Chemistry student at Heriot-Watt University, Edinburgh. Through his university career, he has been able to study in both the UK and in Australia and has taken part in several science outreach projects. The latter of which sparked his interest in science communication.