Positive material identification or PMI is the act of confirming a type of metal alloy based on its chemical composition. This methodology is used in a wide range of applications where the specific chemical composition or grade of the alloy is critical and specific for its end use. PMI is used most commonly in industrial settings where use of the wrong metal alloy grade can result in premature corrosion or even failure of a structure, creating a potentially serious safety hazard. The chemical verification of alloys already in use in various industrial applications often requires that the analysis be non -destructive and performed insitu. The analysis is most commonly performed using a handheld XRF unit often called a "PMI gun" or with a portable Spark-OES instrument.