probably the single most dangerous aspect of the lifestyle, so many ways to do it, such a turn on for many, just be aware of the risks, coz no matter what anyone says, your more than likely going to try some form of it.
i especially enjoy the clear baggie on the head, fastened tight and knowing that i only have a couple of minutes of air, as for brain damage.. well, alcohol too causes that, and kills more people than "edge playing".
moderation is the watch word