Oxygen is not flammable but supports combustion. Oxygen enrichment of the atmosphere, even by a few per cent, considerably increases the risk of fire. Materials not normally combustible in air my burn vigorously or even ignite without any apparent reason in enriched air.
 

• Shut off all engines, electrical equipment and other sources of ignition.
• No smoking or naked lights.
• If available, use emergency equipment stops.
• Stop leaks if possible, especially in enclosed or inadequately ventilated rooms. Move people from area.
• Check all lines and equipment for leaks, with periodic rechecks. All fittings and connections should be properly fitted.
• If leak continues, move cylinder to a safe area and allow to empty.