Jeanne raced across the deck of the wrecked bridge and reached Oliver just as his head hit the floor. She knelt beside his limp body and turned his head, checking that his faceplate had not cracked. It was still intact. That, at least, was good news, but she still didn’t know what had happened to him. Behind the clear faceplate Oliver’s eyes were closed. His cheeks were nearly white and the color in his lips had faded to a pale, sickly blue. Jeanne pressed her hand to his chest and felt that his breathing was rapid and shallow.
“Damn it, Oliver! What the hell is wrong with you?” she muttered.
Jeanne quickly checked his hands, wondering if he had torn his gloves and been exposed to some sort of toxin, but the thick insulated gloves still appeared intact. That made no sense anyway. They weren’t diving in some ocean cave where strange creatures with poisonous spines lurked in crevices. The water in this mine was saltier than the ocean, its only connections to the outside world were far from the sea, and it was completely dark, so there was virtually no chance of any aquatic ecology gaining a foothold in the years since the mine had been flooded.
It’s got to be nitrogen, Jeanne thought. But we aren’t under as much pressure up here in the bubble. Maybe it’s carbon dioxide. She reached for the mix controls built into the tube that ran down the side of Oliver’s neck and tapped furiously at the large switch that would reduce the nitrogen content of his air mix. Looking back to Oliver’s face, she saw no change.
Oh god, his scrubber must have failed.
She slammed the emergency exchange valve on the side of Oliver’s oxygen scrubber, expecting to hear a sudden hiss as the unit disgorged several pounds of bad air and and replaced it with fresh breathing mix from the spare bottle inserted into the side of the scrubber. She heard nothing. Jeanne frantically pressed the button several more times with the same result. She unscrewed the bottle, extracted it from the slot on the side of the scrubber, and held it up to examine in the light of her headlamp. The small pressure indicator on the neck of the bottle showed completely red, indicating that the bottle was empty.
She thought about swapping Oliver’s bottle with her own, but the rebreathers were not designed so that a diver could replace their own emergency bottle while wearing the drysuit. The bottles were intended as an emergency measure. An alarm should have sounded in Oliver’s suit as soon as the rebreather began pulling breathing mix from the bottle.
Jeanne looked around her at the wreck of the ship bridge. They had brought an emergency scrubber canister with them, but it was in one of the dive bags that they had left on the main deck of the barge. Oliver had collapsed nearly a minute ago. There just wasn’t time for her to run back down the rickety steps, to the far end of the barge, and back before he risked brain damage.