In reply to:
I’m renting an SR22 based at SNA and do not have convenient access to the actual AFM. The aircraft is equipped with the semi-portable oxygen tank fitted between the two rear seats. Can anyone tell me the capacity of the bottle? I’m planning a trip and need to do the calculations on duration.
I believe the oxygen you are using in the rental aircraft is the semi-portable 22 cubic foot cylinder from Precise Flight and provides supplemental oxygen for one to four occupants.
Now based on what type of cannulas, masks, flow meters etc… you are using you can find a duration table here.
You will need to check what portable oxygen system you are using in the aircraft you rent to get the correct chart as this one may not reference the model you are using.