Particle impact is a recognized ignition mechanism in oxygen systems. Characteristic elements of particle impact ignition are commonly present in components with large pressure drops (i.e., high-velocity flow) such as pressure regulators, flow control orifices, and flow control valves. WHA International, Inc. (WHA) has performed particle impact ignition testing for various programs using two types of test approaches—transient and steady-state—that are outlined in this presentation. The transient approach involves rapidly introducing high-pressure oxygen into ambient-pressure tubing that is preloaded with metallic particles. Metallic particles are carried by pressure surge through a straight run of tubing and allowed to impact the test article under flowing conditions. The steady-state approach involves preloading metallic particles and slowly introducing high-pressure oxygen through a valve preset in the open configuration up to a closed valve downstream of the test article. Steady-state flow is quickly initiated by opening the valve downstream of the test article intended to control the gas flow. The particle loading area is inspected after the test to ensure that the flow was sufficient to propel the particles toward the test article. WHA evaluated the likelihood of particle ignition during both transient and steady-state approaches by varying parameters such as pressure, particle size and material, orifice size (i.e., gas velocity), and geometry. Test articles included curved tubes, valves, and orifices. Particle ignition was evaluated with video and post-test inspection of the test article and other regions of the test system. WHA observed particle ignitions during tests at pressures from 70 to 276 barg (1,000 to 4,000 psig) and subsonic velocities. Differences in particle ignition activity were noted based on particle material (i.e., aluminum, 300-series stainless steel, and iron). Metallic particles were also found to ignite via ignition mechanisms other than direct particle impact during the transient testing approach.