Promoted combustion testing (outlined in ASTM G124, Standard Test Method for Determining the Combustion Behavior of Metallic Materials in Oxygen-Enriched Atmospheres) is a method for evaluating how metallic materials behave when combusted in environments with high oxygen concentrations, elevated pressure, or both. These tests yield data that are useful for engineers and scientists from a variety of industries who need and rely on oxygen systems. Oxygen compatibility assessments (OCAs) ensure that components are safe for use, and these assessments rely on materials flammability data from promoted combustion testing. However, previous test results are missing significant data for materials that are tested at high pressures above 10 MPa (1,500 psia) and variable oxygen concentrations with nitrogen as the diluent gas. For this reason, the authors posited that conducting promoted combustion testing on materials between 10 MPa (1,500 psia) and 69 MPa (10,000 psia) with various concentrations of oxygen would be useful in future analyses for oxygen compatibility with similar environments, such as nitrox and breathing air. A 3-phase optimal design (3POD) approach was used and was followed by NASA-STD-6001 highest no-burn pressure validation testing to establish a highest no-burn pressure with 10 replicates. Two commonly used materials were selected: 316 stainless steel and 6061 aluminum. To investigate the promoter method used in the study, metallurgical analysis was performed on many rods to observe the posttest resolidified region on the test sample rod.