[Eye of Unk]

Yes thats rather strange, on subs even old old ones there are breathable air manifold fittings all through theboats that you can plug into similar to a mechanics shop air tool plug that they can breath off of.
There is more to the story of course that we won’t really hear about, it could actually be something similar to the Kursk in that they were testing something new and it blew up on them.

[Jonah Hex]

You're likely close. I have a feeling we may find this new suppression system was retrofitted to the Akula IIs to avoid another Kursk-type explosion (i.e. a torpedo fuel explosion causing a massive detonation two minutes later).

All submariners share a common bond and enemy, the sea. My prayers for the lost.