hi! please help im confused, i just want to know if i still need to aspirate air if i want to get the vial's content or should i just inject straight in and aspirate the content? because sometimes i can aspirate the contents straight from the vial with no problem but other times there is resistance and the only way for me to take the solution is to aspirate air then inject the air inside the vial before i can aspirate the content. how will i know if a particular vial needs air aspiration or not? thanks!