Portable X-ray fluorescence (XRF) analyzers, sometimes referred to as an XRF gun, are used to test the chemical composition of materials. Illumination with X-rays causes each element to fluoresce at a characteristic wavelength. By analyzing the pattern and intensity of emitted wavelengths, XRF analyzers can determine the identity and amount of elements and chemicals present in a sample. Handheld XRF analyzers weigh less than 4 pounds, requiring miniature X-ray sources and detectors, but enabling use on-site. Although this small-scale technology limits sensitivity and flexibility, portable XRF analyzer hardware and software can be optimized to detect specific elements and compensate for these limitations. With a handheld XRF analyzer, samples at any location can be tested in seconds and without damage. Handheld XRF analyzers are used by extractive, processing, and manufacturing industries, as well as safety agencies. Applications include testing for lead in paint, sorting scrap metal, assessing mining samples, inspecting imported goods, for art restoration and in testing soil and water quality.