Carpuject!?

My hospital uses the carpuject cartridges, but not the injectors. We draw up the meds into a syringe with a blunt tip and just give it that way. My question is this: do you inject any air into the cartridge? I was always taught no, and that seemed like common sense (such a small space, there's already an air bubble... laws of physics... where's that extra air going to go?). So at work I was drawing up some morphine and I'm not entirely sure what happened but the end of the cartridge popped off and when I showed another nurse she asked if I put air into it and I said I wasn't sure, I wasn't really paying attention... just trying to pull up the med. I think I accidently pushed some air in and that's why it popped off. She thinks I didn't put air into it and that's why it broke. Now there's a huge debate.

SO: yes or no... air into tubex cartridges or not?!