Hello from NY and thanks for looking at my question. I would like advice on what is the best way to identify what refrigerant is being used in a system. I get called to repair problems at walk-in coolers, most are old, abused, dirty and unlabeled, not even a clue written with magic marker. I take the pressure readings and measure the temperature on the tubes in the center of each coil. I look at the P/T chart and see what comes closest to my readings. Is this ok? I worry about NCGs in the system that are upsetting my P/T comparisons. Is there any other method I can use to confirm the identity of mystery refrigerants? best regards