What was found
CLIMBING THRU FL120, THE CREW HEARD A HISSING SOUND AND REPORTED THAT THE CREW OXYGEN QUANTITY WAS DEPLETED. THE QRH WAS FOLLOWED AND THE FLIGHT DIVERTED TO PIT. MAINTENANCE FOUND THE OXYGEN HOSE UNDER THE FIRST OFFICER'S MASK STOWAGE BOX RUPTURED. THE HOSE WAS REMOVED AND REPLACED IAW CRJ200 AMM 35-11-15-000(400)-801. THE CREW OXYGEN BOTTLE WAS ALSO REMOVED AND REPLACED IAW CRJ200 AMM 35-11-03-000(400)-801. THE OXYGEN SYSTEM WAS SERVICED AND LEAK CHECKED GOOD. THE AIRCRAFT WAS RELEASED FOR SERVICE.