A test approach for determining the autogenous ignition temperature of materials in clinical hyperbaric oxygen (HBO2) is presented. This approach was developed because there was no current test approach to specifically evaluate materials for HBO2 service. The testing provides ignition temperatures of materials under HBO2 conditions and is designed to facilitate appropriate material selection. Establishing the difference between the tested material's ignition temperature and the maximum anticipated temperature of exposure in HBO2 provides a measure of the margin of safety—data that is not currently available to material selectors. Although initially designed for HBO2 environments, the test method would be applicable to other low-pressure oxygen equipment and applications commonly utilized by manufacturers of ventilators, hospital manifolds, aerospace systems, and welding/cutting equipment. This paper summarizes the test approach, discusses test variables, and data applications, and it provides considerations for using the test data to help evaluate the oxygen compatibility of materials and the qualification of materials for hyperbaric oxygen.