The whole air thing is actually somewhat of a myth. You need a large amount directly into a vein to kill someone. Obviously don't go pushing air into yourself if you can avoid it. But when I took my "combat life saver" courses in the military the medics purposely left about an inch long air bubble in the line going to the catheter just to show us. And since gear is don't into the muscle you'll be just fine with a small amount.
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