Hi Suncruiser, I can inform you that ..... I haven't the faintest idea.
I'm a licensed engineer specialising in GA/Business aircraft but I think large aircraft wil be similar. The ducting is normally very lightweight; think vacuum-cleaner hose, but not quite as robust. Actual pressure will depend upon demand, but its only going to be slightly above cabin-pressure. Like the output from a domestic fan-heater, or your car's aircon.