The ignition of carbon steel and 304 and 316 stainless steels caused by the impact of low-velocity particles in gaseous oxygen was investigated. A subsonic particle impact chamber was used to accelerate the particles that were injected into flowing oxygen upstream of a specimen of the target material. A standard particle mixture was used that consisted of 2 g of pure iron and 3 g of inert materials. The three alloys appeared to ignite only at velocities high enough to ignite the standard particle mixture. When the particle mixture did not ignite, the three alloys did not ignite either. The oxygen velocity required to ignite the particle mixture was greater than 45 m/s and appeared to be independent of pressure between 4 and 30 MPa. A comparison of these test results and previous test results with the oxygen velocity limits recommended by the Compressed Gas Association (CGA) for oxygen piping indicated that the CGA recommendations are extremely conservative at high pressures and excessively liberal at low pressures.