organic materials generally have lower ignition temperatures than metals considered suitable for oxygen service. therefore the use of organic materials in contact with oxygen should be avoided or minimised, particularly when the material is directly exposed to gas flow. when an organic material must be used for parts such as diaphragms, seals, packing or valve seats, the material with the highest ignition temperature for the required mechanical properties is usually chosen. fluoroelastomers are preferred where large areas are in direct contact with oxygen flow. other materials may be acceptable for static seals where the flow does not come into direct contact with the component.