My dad was a life-long auto mechanic before he retired... he once had a bad battery (broken post inside the battery, but nobody knew) blow up on him. Car wouldn't start, so he went to wiggle the terminal on the post... BOOM. Whole top of the battery blew off!
His first reaction? He crossed the whole width of the shop (about 75 feet) in like 4 seconds, grabbed the water hose out of the car-wash man's hand, and sprayed himself in the face and the chest, all over where the battery acid had sprayed on him. Barely got anything worse than something that looked like a sunburn. Lucky he thought to GET IT OFF OF HIM, that fast!
My uncle (Dad's brother) used to work with him... he created the SECOND most hazardous situation I've seen in an auto shop. Was working on the air conditioning of a car... had it running, while adding Freon. The hose came off, and Freon sprayed RIGHT INTO THE AIR CLEANER. Two guys were goofing off, sitting on the back bumper of the same car... they started coughing and choking, and stumbled off, outside, gasping for air. Turns out, when you combust Freaon inside an engine, you get PHOSGENE GAS... ie MUSTARD GAS!! Fortunately, neither of the two goof-offs were permanently injured!
The MOST dangerous situation I've ever seen, happened in the old shop my Dad worked in, before they moved to a new building... there was an in-the-floor waste-oil tank, where they put the oil that came out of cars during oil changes. You were NOT supposed to put anything with gasoline in it in there... but sometimes, people would pour small amounts of dirty gas (left over from rebuilding a carb, etc) in there. One day, one of the idio... er, mechanics was actually WELDING something next to the oil tank... and a welding spark went right down the funnel, into the tank. RRRUMMMBLE... BOOOOOOOOMMMM! Looked like an upside-down rocket engine! Flames shot out like 10 feet out of the neck of the tank! The funnel actually got stuck IN THE CEILING of the shop, from the rocket blast!!
Fortunately nobody got hurt, and nothing even really got damaged, with the exception of the funnel, which was pretty much junk...
Worst thing that happened to me, personally... had a hood up on a car, and the hood prop failed (came out of the socket) and the hood fell. Caught the end of my finger, between the hood and the fender. Had to wait until someone else could come over and un-latch the hood, to get loose! Fortunately, it just bruised the hell out of my fingernail, that was all!
Regards,
Gordon.