A creative experiment shows what happens when gas in a sewer explodes.
After creating a mini replica of a sewer pipe network out of transparent tubes, then filling them with flammable gas, the person carrying out the experiment lights the gas at the open end of one tube.
The flame is then shown to travel through the pipe network before exploding out into the open at the network's opposite open ends.
This replicates the situation sometimes found in sewers where gas has accumulated before someone drops a lit cigarette or firecracker into it.
