Never let it happen myself, in my old Metro I used to keep a jerry can full of petrol in the boot, one of those green plastic ones. One day as I was driving around town I started to feel light headed and my legs felt weak. I made it home, got out and was fine once I'd had some fresh air. I looked in the boot and the can had fallen over, the top had somehow come off and it had soaked the entire boot.
I'd been driving round breathing in petrol fumes for about 10 minutes. :yuck:Luckily I had the windows down anyway.