What is the air lock technique?

Answer 1

It's a technique in parenteral medication used frequently in intramuscular sites.

Holding the syringe upright, the administrator of the medication aspirates around 0.2ml to 0.3mL of air in order to clear out any medication that may be left inside the needle.

They usually change the needle after this so that no solution of the medication remains outside the needle shaft.

Injection of the needle is done at 90 degrees so that all of the air you aspirated should be the LAST to exit the syringe, creating an air lock inside the skin.