Yanno those disposable O2 hoses w/ the threading that come w/ Ambu Spurs?
Had a full arrest w/ myself, and a half dozen firemen w/ no prior first aid training. I was blindly explaining how to hook the BVM to the cylinder, when I heard a loud hiss and a sharp POP. Looked over, and he had screwed this threaded hose onto the DISS port of the cylinder and it caused the reservoir bag on the BVM to pop.