You beat me to it. Employers and insurance are usually all over this. It's hard to keep guys like this from abusing compressed air, because... well, farts man.

Rupture of the Sigmoid Colon following Compressed Air Injury: A Case Report

"Abstract;The case is a man of 33-year-old. The air was jetted in state that pressed against an anal region, when it wore working cloth in respect of air compressor by romping about, and the traumatism was done. He was carried by intense abdominal pain and abdominal distension in the emergency to the hospital. By thoracicoabdominal part simple x-ray inspection, it was diagnosed with intestine perforation, since there was the large free gas in peritoneal cavity, and the emergency operation was carried out. There was lacerated wound of contralateral taenia coil of intestinal membrane from the sigmoid colon over the rectum. The large intestine of part of damage was partially resected, and artificial anus was created. The attention was needed for the operation method without guessing the damage of the mucosa side in the observation from the chorion plane."

http://bit.ly/iIvGb

Sorry, that was meant to be a reply to kennydra.

A guy at one of my dad's old machine shops wound up in the hospital from an ass-related compressed air injury. They'd shoot each other in the butt whenever they opportunity presented itself.