I read in the proper injection sticky that you could inject up to 10ccs of air without consequence. I've personaly been told by Docs and Nurses you would never want to inject more than 3ccs of air. Maybe the 10ccs applies to IM and the 3ccs applies to IV, I don't know. I'll ask my HRT Doc next time i see him in a month or so. I personaly try not to inject any air, but i don't get worked up over a few small air bubbles. I use the Z method although I don't use 2" or 3" needles so maybe my way is not making any difference, but I'll personaly stay away from the 2 or 3 inchers.