Choosing a seal material for Oxygen, Hot
The table above rates every common O-ring elastomer for service in Oxygen, Hot on an A–D scale. A is Excellent, B is Good, C is Fair (test before relying on it), and D is Not Recommended. An X indicates insufficient published data.
For Oxygen, Hot, the strongest candidates are Fluorocarbon (Viton), Perfluoroelastomer, Silicone, Fluorosilicone. These ratings are representative at ambient conditions (~20°C). Compatibility shifts with temperature, concentration, pressure and exposure time, so always validate the material against your real operating envelope before committing to a design.