How fires can start

Was in the garden Sunday and heard a loud bang cylinder/can explosion type from the field at the rear of my place,had a look through the trees expecting to see youngsters exiting some sort of fire and explosive experiment (been there!)no one to be seen.
Back to gardening, then, smell of smoke,the field of straw was on fire and heading my way so called the fire service who arrived in a few minutes and extinguished the blaze.
Cause was a helium filled party or event balloon which had some some sort of metal looking surface had gone across the mains electricity wires,went bang and the remnants dropped to the floor and started the fire.
Excitement over but just shows you never know what to expect.

once had a glass bottle on the seat of my van,hot sunny day yes the seats caught fire luckily i spotted the smoke not too much damage ,headlining and surface damage to the passenger seat,the only problem i was working in a yard with fuel tankers in close proximity