During this crisis, there had been ongoing conflicting reports on how much air the trapped crew of AS28 had to survive on. Bubblehead noted this here in a Reuters article from early Saturday:
"We must complete the operation in 24 hours because the supply of air on board is not without limit," Interfax news agency quoted the deputy chief of navy staff, Vladimir Pepelyaev, as saying.
"It is believed that there is still enough air for slightly more than 24 hours," Pepelyaev added. Initial offical reports said the AS-28, itself a rescue vessel, ran into trouble when its propeller became entangled in fishing nets during a military exercise. They said it had five days' supply of air -- more than enough for any rescue mission.
However, about 1100 BST on Friday, naval spokesman Igor Dygalo said the trapped vessel had only 24 hours' worth of air left. There was no official explanation why estimates of air remaining still stood at 24 hours on Saturday morning.
This submersible was primarily submarine rescue vehicle and therefore the crew would have been trained in all aspects of submarine rescue problems, including air quality and conservation. Once the crew knew that they needed to await outside rescue that training would have kicked in and may have been what pushed the air supply to the more optimistic estimates.
If my experience with doing restoration work on the old Soviet Juliett 484 is any indication the Russians kept an ample supply of lithium hydroxide for CO2 absorption. They may also have kept chlorite candles chemically similar to what is in an OBA for emergency O2 generation on board their submarines. It would be reasonable to think that this practice would include a submarine rescue submersible if not for its own use then to supplement a submarine on the bottom. Any submarine rescue vehicle would require multiple trips to a stricken submarine to effect a complete crew rescue.
As far as the political air is concerned, Putin and some Russian admirals can get some sleep tonight. It would have been a political crisis similar to that of the Kursk if things had come out differently, for the sake of the AS-28 crew, thank god and the Brits ROV team it didn't.