Aircraft Flight Operation Regulations Article 302

The use of oxygen aboard aircraft shall meet the requirements specified in Article 77, 78, and 123.At flight altitudes above flight level 350 unless one pilot at the controls of the aircraft is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the aircraft exceeds 14,000 feet (MSL).While at or below flight level 410, the pilot need not wear and use an oxygen mask if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed. If for any reason at any time it is necessary for one pilot to leave the controls of the aircraft when operating at flight altitudes above flight level 350, the remaining pilot at the controls shall put on and use an oxygen mask until the other pilot has returned to that crew member station.