It runs at atmospheric pressure (Air or He gas). The advantage of using atmospheric pressure is that powders and liquids can be analyzed, in special sample holders. The disadvantage of using an atmosphere instead of vacuum is that light elements (F or below) cannot be detected. Also, an energy dispersive detector has poorer element separation than a wavelength dispersive system (WD-XRF) has, so the results are not fully quantitative. But they can me made accurately quantitative by creating standards and calibration curves corresponding to the analyzed material. The analysis time is relatively short (10-20 minutes) so the instrument works well for quickly assessing materials from in-house experimental work.