Decibel damage.
Yeah, you guys have to watch out for damage from the high pressure levels.And I mean to yourselves not hte car. Starting at 130dB permanent hearing loss is assured (over time, not instantly). At about 150 dB it can rupture smaller blood vessels (nose bleeds, red spots in your eyes), and can easliy rupture your ear drums. Also at about this level it can (as you already found out) cause you to pass out. The extreme pressure levels makes it impossible to breathe. Your body depends on a small pressure gradient between inside and outside your body to be able to breathe. If the pressure gradient is too high, it forces air in or out of your lungs. With most music, it happens so fast that you just can't get enough oxygen. At about 160dB permanent damage can happen at many places i your body. And finally, at about 180 dB, the pressure starts to rupture organs. That's when you're screwed.
The Army is actually trying out "non-lethal" weapons based on sound waves. It projscts sound in a cone at about 150-170 dB and knocks people unconscious. Good for crowd control, etc..
Hope this was informative, sorry if it was too long winded.
And guys, please be careful. A little loud music today can ruin your hearing forever. You don't want to be using a hearing aid at 40. At 60... well let's just say you won't be enjoying much music anymore. (sorry, had to preach)