Removing the air line from the push to connect fitting is a relatively simple process. How our fittings work, is once the air line has been pushed into the fitting, there are small teeth that hold the air line in place. When removing the air line from the fitting, the goal is to release these teeth allowing the air line to come out. You will notice on the fitting there is a collared end where the air line inserts into the fitting. This collared end is what releases the teeth holding the air line in place in the fitting. What you will need to do is first push the air line into the fitting, and while keeping pressure on the air line, pull back on the collared end of the fitting, opposite of the direction you are pushing on the air line. Once you have pulled the collared end of the fitting back towards itself, the teeth should release, and you should then be able to pull the air line out of the fitting.