These do seem all within the range of possibilities.
The bag is old and imperfect, and I don't think it is completely airtight either. Not as much from permeability of the polymer but phyical wear & tear too.
I smelled the exhaust when I deflated it the last few times and it is very faint but industrial. Doesn't smell like mold but organisms could still be hidden somewhere breaking down plastic or additives. Which may or may not consume oxygen.
Osmosis I have been considering too, if fairly high molecular weight breakdown products are gradually emerging into the gas phase, with the bag way more permeable to atmospheric gases, maybe the atmosphere is forcing its way in and builds slightly higher partial pressure than ambient as a molar dilutive effort.
This is a good time to put the floppies in a brand new bag and see what happens, the experiments never end ;)
The bag is old and imperfect, and I don't think it is completely airtight either. Not as much from permeability of the polymer but phyical wear & tear too.
I smelled the exhaust when I deflated it the last few times and it is very faint but industrial. Doesn't smell like mold but organisms could still be hidden somewhere breaking down plastic or additives. Which may or may not consume oxygen.
Osmosis I have been considering too, if fairly high molecular weight breakdown products are gradually emerging into the gas phase, with the bag way more permeable to atmospheric gases, maybe the atmosphere is forcing its way in and builds slightly higher partial pressure than ambient as a molar dilutive effort.
This is a good time to put the floppies in a brand new bag and see what happens, the experiments never end ;)