Fire incidents involving oxygen piping and associated equipment that have occurred below the exemption pressure threshold (per the European Industrial Gases Association [EIGA] 13/12 and the Compressed Gas Association [CGA] G4.4 standards) might motivate exploitation of additional, nonexplicit information gathered from the ASTM G124 promoted ignition and combustion test (PICT). For that, it is necessary to analyze quantitatively the complete sequence of phenomena involved in ignition then transition to propagation. First, we consider the elementary heat and mass transfer/oxidation system extending over a small depth beneath the cross section of a rod-shaped sample, heated fully controllably by an incident laser beam in gaseous oxygen. An oxygen jet flow at normal incidence reproduces the dynamic pressure condition that would occur from a local flowing pattern on a surface element of a hollow body's inner wall in a real-life system. In situ, real-time diagnostics include high-speed imaging and temperature measurements by optical pyrometry. Parameters are laser power (maximum 3–4 kW) and time of exposure to radiation, oxygen flow velocity (1 to 60 ms⁻¹), and pressure (1 to 21 bara). The investigated parametric domain represents thousands of experiments for carbon steel and stainless steel. Ignition occurs at a characteristic critical temperature, corresponding to thermally induced loss of integrity of the primarily formed passivating oxide; although, in the case of stainless steel, a particular multistep mechanism is involved. The amount of deposited energy necessary for ignition is reduced when laser power is increased. Oxygen jet flow velocity and pressure have a negligible effect on ignition energy. Beyond the limits of this geometry (selected initially for simplicity), we now have a robust quantitative methodology for transposition to investigating puncture ignition and breach expansion for a pressurized hollow vessel, as well as the details of physical mechanisms in PICT.