DECONTAMINATION
Prof. Renato Bonora reviews Large Volume Decontamination (LVD-X) to overcome internal chemical contamination within buildings
(cell) was a stainless steel cube, the inner side 5 cm in length with a total inner volume of 125 cm3. A gastight bushing holding the axis of a 6V low-speed propeller stirrer was integrated into the top of the cell (opposite, top leſt ). A sheet of fi ltration paper, with a drop of 10 µL of CW agent, in a watch glass was placed in the centre of the contamination cell. The cell was then placed into the environmental chamber with the ventilator on. Aſt er the contamination process (30 min), the contamination cell was opened and the substrate samples transferred for liquid extraction or into evaporation cells.
Positioning of the samples inside the testing chamber.
LVD-X Experiments The experiments were performed inside the special testing chamber (overall volume: 20.121 m3
, inner surface walls: 45.335 m2). Dimensions of the testing
chamber were: Length – 3.65 m, Width – 2.25 m and Height 2.45 m). Samples were placed on the testing chamber walls 1.5 m above the ground in four special holders inside the chamber. Two sets of four vapour contaminated substrate samples were placed on the side and front walls of the chamber. (opposite, top right) The LVD-X aggregate was placed
LDV-X Aggregate. Above leſt : Open contamination cell with propeller stirrer with sheet of fi ltration paper on the watch glass for liquid agent deposition (during contamination phases the panels are sealed on the windows cell).
the hydroxyl radicals. These in turn are generated by the
catalytic decomposition of hydrogen peroxide in the application device through a heterogeneous metal catalyst, combined with UV radiation. Due to its instability, the hydroxyl radical must be generated continuously during application. The sample panels (Table 1 overleaf) were contaminated with an appropriate amount of vaporized CW agent and the density of the aerial contamination recorded per required parameters. The
panels were then exposed to LVD-X decontamination technology. The parameters were then determined aſt er the sample decontamination process in accordance with NATO documentation and standards. CW Agent vapour was absorbed into
the structure of each substrate. For uniform and reproducible contamination of substrates, the conditions at the time of exposure and the concentration of vapours of CW agents were precisely recorded. The contamination container
CHEMICAL WARFARE AGENTS (CWAS)
Measured samples of three types of CWAs were employed for testing: ❶ Sulphur Mustard, (bis [2-chloroethyl) sulphide], hereinaſt er HD agent, purity 98.5 %
❷ Soman, O-pinacolyl methylphosponofl uoridate, hereinaſt er GD agent, purity 90.6 %
❸ Sarin, Isopropyl methylphosphonofl uoridate, hereinaſt er GB agent, purity 98.7%
Agents 4 were chosen as they are easily optimized for contaminating critical infrastructure via air fi ltration.
outside the testing chamber (p. 58, right). The fi xed directional spraying nozzles was placed inside the chamber at a height of one meter, with the angle of the aerosolized stream orientated towards the samples fi xed on the front wall. The LVD-X aggregate was enabled to spray the activation water mixture and active hydroxyl radical decontamination solution, either simultaneously via both pipelines, or consecutively, starting with the water mixture. The simultaneous deposition was used for testing purposes.
Sampling and analytical procedures Eight experiments were replicated to determine CW agent vapour contamination density on each type of substrate panel. Four of them have been decontaminated. For each experiment, liquid was extracted by ultrasonic bath into an n-hexane solvent. The total CW agent was then determined by Gas Chromatography analysis of the liquid sample. Data reported in Table 3 overleaf refers to average data of the four samples (2 front, 2 side position).
GB agent vapours initial contamination Initial contamination results show signifi cant diff erences between the tested substrate panels’ contamination density when exposed to GB agent vapour. The contamination density on Chemical
CBNW 2013/02 59
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