Positive material identification or PMI is the verification of metal alloys based on their chemical composition. This methodology is used for a wide range of applications where the grade of metal alloy used in a particular application needs to be confirmed. PMI is used in a wide range of applications, but most commonly in industrial settings where using the wrong metal alloy grade can result in premature corrosion or even failure creating a potentially serious safety hazard. The chemical verification of alloys already being used in industrial applications often requires that the analysis be non -destructive and performed insitu. This is most commonly performed using a handheld XRF unit often called a "PMI gun" or portable OES instrument.