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The explosive chemistry that cleans up your car exhaust

Without platinum, city air would be unbreathable. This rare and precious metal is the magic ingredient in the catalytic converter that helps to burn up all the nasty gases in your car exhaust.

Here, Professor Andrea Sella of University College London demonstrates the explosive chemistry behind catalysis to the BBC's Laurence Knight.

Filmed at the laboratories of "cat" manufacturer Johnson Matthey as part of the Elements radio series on BBC World Service.