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The COGen consists of two PVC chambers (‘A’ & ‘C’, Fig 6.7). The inner chamber “A’ is mounted to the screw lid of the larger outer 10cm (3.9 inch) container and has a drip exit ‘F’ in its base. The drip rate is controlled by a screw ‘E’.
150 ml of 85% formic acid is placed in chamber (‘A’) with the control-valve shut.
250ml of concentrated sulphuric acid (98%) is placed in the outer chamber ‘D’ and the COGen assembled.
Opening the screw ‘E’ allows the formic acid to drip into the concentrated sulphuric acid. Copious amounts of carbon monoxide are released and exit the chamber through vent holes in the lid ‘H’.
The Video shows the COGen being armed and placed in a small car. The carbon monoxide concentration in the car was continuously sampled with a probe positioned near the head of the mannequin. The graph (Fig 6.8) shows the measured concentration in ppm, plotted over the first 30 minutes. Lethal concentrations were reached a few minutes after switching on the generator. A peak level of ~3% CO was recorded.
Sourcing the Acids
Concentrated sulphuric acid (98%) can be purchased from chemical suppliers or at hardware stores where it is sold as a drain cleaner. Concentrated laboratory sulphuric acid is an oily clear liquid, whereas the drain-cleaner sulphuric acid can be dark brown in colour because of additives, but this does not effect the generator’s operation.