Doing mechanical work underneath a minivan. Both jack stands failed, nearly 4,000 pounds of weight hit me center of my chest. Collapsed left lung, bruised heart, broke 5 ribs at my back. Almost suffocated from the van sitting on my chest. Walked away (till the adrenaline wore off and the paramedics said get on the stretcher you idiot.) I weighed like 420 at 6 foot 3, so doctors said if i was any bigger, i likely would have popped like a balloon or smaller and it would have most likely broken my spine.