A man goes skydiving.
After he jumps out of the plane he pulls the parachute cord and nothing happens.
Panicking, he pulls the emergency chute. Again nothing happens.
As he is plummeting towards the earth he sees a speck moving up towards him. As he focuses he can see it's another man, his clothes smoking and his hair singed.
As they pass the skydiver shouts 'Do you know anything about parachutes?'
The singed bloke replies 'No, and I don't know anything about f**king gas boilers either'!