Post-Contamination Vapour Hazards from Military Vehicles Contaminated with Thickened and Unthickened GD

The residual vapour hazards from four types of military vehicles previously contaminated with either thickened or unthickened GD have been measured over periods up to 72 hours. The effects of decontamination procedures, the use of impermeable paint, vehicle design and climatic conditions on the magnitude of these hazards have been investigated and an assessment made of their relevance to contamination control. It was found that on permeable surfaces, e.g. alkyd paints, liquid GD had disappeared after approximately 30 minutes and decontamination procedures applied 15 minutes after the contamination had been applied were ineffective in reducing the subsequent vapour hazard the vapour hazard arising from thickened GD contamination was less than that encountered with liquid GD. The employment of decontamination procedures following contamination of inservice military vehicles with thickened and liquid GD produced no significant decrease in the subsequent vapour concentrations. On impermeable surfaces, e.g. polyurethane paint, liquid GD persisted for longer periods at least 3 hours and hence decontamination was relatively more effective in reducing the immediate post-contamination vapour hazard but even in this case weathering alone for 3 hours had the same effect as weathering alone on an alkyd-painted vehicle. In the case of thickened GD on polyurethane-painted vehicles it was observed that the agent persisted on the surface for up to 5 hours.