Charging hoses can contain up to 1/2 ounce of freon. If air is inside, it
can contain a gram or two of moisture.

First, attach youur charging hoses to the service ports.Screw thenm on only
part way,though. Not enough to open the valve core. Next, open up the valve
that will allow freon to rush out. Do this for about 1 second(this is legal
to do).It will push outthe air and moisture from the hoses. Finally,
immediately finnish tightening the hoses to the service ports.

Now you can charge away.