The resistance of fire-fighting foams to destruction by petrol

The rate of drainage of a foam layer on the surface of petrol has been measured for a range of petrol temperatures, with different types of foam compound. In the experiments described, the liquid resulting from the breakdown of the foam was collected after it had drained, and a ‘petrol resistance index’, defined as the time in which 25% of the liquid content of the foam could be collected, was calculated. This index was found to vary greatly with the temperature of the petrol and the type of foaming agent employed.