Unless you've got a physical or mental condition you should not die after blackout.
You're body blacks out because of lack of oxygen, intensity etc. when it blacks out natural processes take over and breathing should resume B|
I would imagine sleep apnea, or some sort of heart or lung condition could fuck with that though. But if you're healthy blacking out from intensity (not holding your breath) probably shouldn't be anything to worry about. If it's from not breathing, i'd suggest breathing exercises or seeing a Gyno ._. / physician with questions and description