Why chemical simulants?
The training of professionals in the detection and decontamination of chemical warfare agents is essential because it enables the development of gesture, organization and use procedures for the various PPE and detection and decontamination devices. It also allows the practitioners to be placed in the psychological conditions that they would encounter in the reality.
These exercises cannot use real chemical warfare agents because of their dangerousness. It is therefore necessary to use so-called “simulants”, which are very close to the real agents but without toxicity. They will bring us closer to reality in terms of detection and decontamination.
The ideal chemical simulant
The ideal simulant must have and combine the following properties:
– Physicochemical properties as close as possible to the real agents (consistency, colour, solubility, persistence, volatility, odour, etc.);
– Easily spotted with the naked eye (coloration, fluorescence…);
– Ante and post decontamination detection identical to actual agents using paper detectors and field devices (flame spectrometers, ionic mobility, AP2C, AP4C…);
– Non toxic to humans (skin and respiratory system) and can be used in any condition (interior, exterior);
– Decontaminable by the common products and protocols used;
– Non toxic to the environment or biodegradable (do not have to take care of the land when you leave).
Numerous studies of chemical simulants such as Shanonn L. Bartelt-Hunt et al. (1) compare the molecular structures of chemical agents and their main simulants. Physicochemical properties are also indicated as well as adsorption coefficients, biodegradability, hydrolysis and toxic properties.
These chemical agents must be detected by analytical instruments and therefore possess the appropriate chemical function. In the case of AP4C, – S for HD, P for G and V, P and N for GA (tabun) and VX… Detections with paper detectors must also be equivalent.
The different properties of all these products are also compared in the publication by J. Lavoie et al. (2).
The simulant must be visible to the naked eye in order to detect cross-contamination. Fluorescence or chromogenic aspects may be the result of coloured or fluorescent products added or not. We can read the studies of KJ. Wallace et al. (3), V. Kumart and E. V. Anslyn. (4) and A. M. Costero et al.(5).
The simulant must lose its main chemical function by degradation during decontamination in order to make it invisible to the detectors (same for coloured or fluorescent marking); the degradation products have been well studied by A. B.. Kanu et al. (6).
The physico-chemical properties such as viscosity and vapour pressure of the simulant should be closest to the real products. It is mainly the solvents used that will achieve this result.
The simulant may therefore be made up of several different molecules, each providing an element such as: detection (Atome S for HD…), visual identity (colorant, fluorochrome…), physical appearance (consistency, colour, solubility, persistence, volatility, odour…), non-detectability after decontamination and non-toxicity.
Current chemical simulants
The simulants used for training purposes are relatively few on the market: TOXsim (OWR) (the simulants are non-toxic, UV detectable but far from war chemicals), TrainSaf® (the same simulant is available in 3 versions whose physico-chemical properties mimic those of the 3 products G, H and VX, detectable under UV and non-toxic they are nonetheless not representative of the real products and are not identified in a characteristic way by the usual detectors, Flir (USA) (a training simulant reacts with the corresponding enzyme detector. The possibilities seem limited).
Sim-Kit [1] (Ouvry SAS)
Each simulant is well individualized and its physico-chemical properties are very close to those of the real agent.
HD-SIM yperite simulant: the main component is methyl salicylate. The final product is an oily yellowish liquid, which spreads rapidly or produces droplets on the surface. Non-soluble and denser than water, it has the same persistence as the HD agent. Low volatility at 20°C. Red with paper detector it gives the same profile as HD with field sensors. It contains a fluorescent tracer visible under UV lamp.
VX-SIM simulant of VX :the main component is polypropylene glycol monobutyl ether. The final product is viscous, yellow-brown, it spreads quickly on the surface. It is not soluble in water and gives a green color on the detector papers and a V profile on the field detectors. Its volatility is very low at 20°C and it contains a fluorescent tracer visible under UV lamp.
GB-SIM simulant of sarin: dipropylene glycol monomethyl ether (DGPME). Colourless, it spreads easily on surfaces. Its persistence is similar to that of GB. It is very volatile at 20°C and gives a yellow colour on the detector papers and a characteristic profile with field detectors. It contains a fluorescent tracer visible under UV lamp.
The use of PDF1, CALID 3, Anachemia, and the use of flame or ionic mobility spectrometers, detection, alerting and identification devices (AP2C, AP4C, CAM, RAID or RAID-M/M100, LCD3.3,…) make the exercises more realistic with improved performance in terms of speed, precision and ease of use.
The simulants are distributed in easy-to-use 20 mL drop-count bottles. A compact, shock-proof and waterproof SIM-KIT ® case allows samples to be transported and the UV lamp used to detect fluorescence of simulants (provided with).
It should be noted that the formulas of the various simulants have been changed. Fluorescent agents have been added for two purposes: to visually identify the agents on surfaces by means of the UV lamp provided and to easily distinguish a maliciously spread simulant from a real agent. In addition, the new optimized formulations have been eliminated from the list of chemicals that may be carcinogenic, mutagenic and toxic to reproduction (safety data sheets are provided with the Kit).
Nevertheless, the use of these simulants must be done in small quantities and under safe conditions involving the wearing of vinyl or nitrile gloves and a pair of protective goggles. Indoors it is recommended to ventilate the room properly.
Ouvry recently acquired the SIM KIT ® patent [2] from the Dutch Hotzone Solutions Group.
The contribution of simulations in the field of CBRN has been well analysed in this publication [3] published by Christian Leonce.
1- S.L. Bartelt-Hunt, D.R.U. Knappe, M.A. Barlaz. A review of chemical warfare agent simulants for the environmental behavior. Critical Rev. Environ. Sci. and Technol., 2008, 38, 112-136.
2- J. Lavoie, S. Srinivasan, R. Nagarajan. Using chemonformatics to find simulants for chemicals warfare agents. J. Hazard. Mater. 2011, 194, 85-91.
3- K.J. Wallace, J. Morey, V.M. Lynch, E.V. Anslyn. Colorimetric detection of chemical warfare simulants. New J. Chem, 2005, 29, 1469-1474.
4- V. Kumart, E.V. Anslyn. A selective and sensitive chromogenic and fluorogenic detection of a sulfur mustard simulant. Chem. Sci, 2013, 4, 4292-4297.
5- A.M. Costero, S.Gill, M. Parra, P.M.E. Mancini, R. Martinez-Manez, F. Sancenon, S. Royo. Chromogenic detection of nerve agents mimics. Chem. Commun, 2008, 6002-6004.
6- A.B. Kanu, P.E. Haigh, H.H. Hill. Surface detection of chemical warfare agent simulants and degradation products. Anal. Chim. Acta. 2005, 553, 148-159.