Why must recycled refrigerant be checked for air?

Air is considered a contamination in an A/C system. This is because it is a not a condensable gas.

This means that the type of pressure that the A/C can reach is not sufficient o condense the air from gas to liquid.

As a result, air will only be occupying space and displacing the refrigerant which will lead to a poor performance of the whole system and can even lead to total failure of the system.

This poor performance can be in terms of:

1 - evaporator freeze-up

2 - noise

3 - reduced cooling performance

4 - higher discharge pressure