DTG
First of all the source for your previous post regarding your collegue is the correct one and you are a true gentleman, thank you for your pm.
I take back my critisism of your colleagues source, I still do not agree with the statement, but we will research it.
I am aware of the certification requirements for pressurization, but the limiting factor is not DUAL PACK FAILURE (you would only get a cabin rate of climb of about 650 to 800FPM); the limiting factor is explosive decompression.
Lets say you are at FL390, both packs fail, you need to descent to 14,000' (descent 25,000') you can descend at an average of 4,000 FPM (not very steep) it will take you a little over 6 minutes. Lets say the cabin for some reason was at max alt 8,000 and will climb at a max of 800 FPM (6,000 to 14,000) it woul take 7.5 minutes. All conservative numbers
If the certification was based on single pack operation at FL310, there would be a procedure or ECAM when one pack fails to limit the ceiling to 310.
BTW, FAA Part 135 is Air Taxi, this would not apply for certification, more so for operation under Part 135.
G