Chapter 2: The Blow-Down

The hatch was sixty centimetres in diameter, and you entered the chamber the way you entered every confined space in the offshore industry: feet first, arms raised, a controlled descent into steel.

Kwame went third. Mac had gone first, as Mac always went first, with the unhurried economy of a man who had been entering chambers since before Kwame had left Accra. Then Fraser, then Kwame, then the other three — Tomasz, a Polish diver who had been doing saturation work in the North Sea for eight years; Sean, an Irishman from Cork who talked more than any other diver Kwame had worked with and who, in the helium atmosphere they were about to enter, would sound so absurd that even he might be reduced to silence; and Davy, a Geordie, twenty-eight, on his sixth sat rotation, still new enough that the blow-down made him nervous and experienced enough to know that the nervousness was appropriate.

Six men. One chamber. Twenty-eight days.

The living chamber smelled of disinfectant and recycled air and the particular metallic note of the CO2 scrubbers — lithium hydroxide canisters that absorbed the carbon dioxide from their exhalations and released a faintly alkaline residue into the atmosphere. The scrubbers were changed every twelve hours by the Life Support Technician, passed through the medical lock in sealed bags, the used canisters heavy with the accumulated breath of six men.

The bunks were stacked three high on each side of the chamber, each one a foam mattress on a steel shelf, each one separated from its neighbour by perhaps thirty centimetres of vertical space — enough to roll over, not enough to sit up. Kwame took his usual bunk: port side, middle tier. He had an irrational preference for the middle — neither the top bunk, where the heat collected and the fluorescent light was closest, nor the bottom bunk, where the condensation sometimes dripped and you could feel the chamber's hull against your back, cold as the ocean it was designed to resist.

Mac took the bunk opposite. They had shared this arrangement for five years, sleeping less than two metres apart in a steel cylinder, breathing the same processed air, hearing each other's sleep sounds with an intimacy that neither of them would have chosen but both had accepted as a condition of the work. Mac snored. Kwame ground his teeth. They had discussed neither of these facts and never would.

The living area occupied the forward half of the chamber: the bunks, a fold-down table bolted to the deck, two bench seats. The aft half held the shower — a trickle of lukewarm water that was never enough — and the toilet, which was separated from the living area by a curtain that provided visual privacy and no acoustic privacy whatsoever. There was a television screen behind a pressure-rated viewport, connected to a media server topside. There was a shelf of dog-eared paperbacks left by previous rotations. There was a microwave, specially sealed for hyperbaric use, for heating the food that was passed through the medical lock in insulated containers.

This was the space. This was all of the space. Twelve metres long, three metres in diameter. For twenty-eight days.

Gary Hendricks's voice came through the communications speaker, tinny and distorted by the intercom system: All personnel confirmed in the living chamber. Preparing for blow-down. Confirm all hatches sealed.

Mac checked the trunk hatch — the connection between the living chamber and the transfer chamber. Sealed. Kwame checked the medical lock. Sealed. Fraser checked the secondary medical lock. Sealed.

All hatches confirmed sealed, Mac said into the intercom.

A pause. Then: Commencing blow-down. Target depth one-five-zero metres. Compression rate one metre per minute for the first fifty metres, then point-seven-five metres per minute to storage depth. Estimated time to saturation depth: three hours twenty minutes. All personnel, clear your ears regularly. Report any discomfort immediately.

One metre per minute. The pressure would increase at the rate of one-tenth of an atmosphere every minute — a rate that allowed the gas to dissolve gradually into the body's tissues, the nitrogen being replaced by helium as the breathing mix shifted from air to heliox, the slow saturation of blood and muscle and fat and bone with inert gas that would take days to release once the process was reversed.

Kwame sat on his bunk. He braced his feet against the deck. He closed his eyes.

The hiss began.

It was a sound he knew better than most sounds in his life — better than the rain on Aberdeen's granite, better than the call to prayer that drifted over Osu from the mosque on the Accra-Tema road, better than his mother's voice on the phone, which he heard so rarely that each call felt less like a conversation than a proof of concept, a demonstration that the technology still functioned, that the distance could still be bridged, if only technically.

The hiss was helium entering the chamber through the supply valve in the overhead. It was a thin, constant, penetrating sound, and it changed everything. The pressure gauge on the chamber wall — a simple bourdon tube instrument, analogue, because analogue gauges did not fail the way digital instruments could — began to climb. One point one atmospheres. One point two. One point three.

Kwame swallowed. His ears popped. The Eustachian tubes opened and equalised, a micro-adjustment the body made automatically if you allowed it to, if you did not clench against the pressure but relaxed into it the way you relaxed into a current at depth — not fighting, not yielding, but finding the angle at which the force passed through you with the least resistance.

The chamber temperature rose. Compression heated the gas — a fundamental property of physics that no amount of engineering could fully compensate for. The life support system pumped chilled water through cooling coils in the chamber walls, but there was always a thermal lag, and during the blow-down the temperature could climb to thirty-two or thirty-three degrees before the cooling caught up. The men sweated. The humidity spiked. The scrubbers worked harder.

At two atmospheres — the equivalent of ten metres of seawater — Kwame felt the first headache. It was a compression headache, caused by the pressure differential across the sinuses, and it would pass as the tissues equalised, but for now it sat behind his forehead like a thumb pressed against the bone, a reminder that the body was not designed for this, that fifteen atmospheres of pressure was a condition the human organism had never evolved to tolerate, and that every minute they spent at depth was a minute spent in a state that required constant mechanical intervention to survive.

Mac was reading. Of course Mac was reading. Mac read during blow-downs the way other men watched the pressure gauge — with steady, unperturbed attention, as though the increasing pressure were a weather condition rather than a fundamental alteration of the physical environment. He was reading a Tom Clancy novel, the same Tom Clancy novel he had been reading for what Kwame estimated was three rotations, either because he was a slow reader or because he kept losing his place or because the book had become a talisman, a familiar object carried into the unfamiliar, the way a child carries a stuffed animal into a hospital.

Kwame did not ask. You learned in the chamber what not to ask.

At fifty metres — six atmospheres — the gas mix was fully heliox: ninety-six per cent helium, four per cent oxygen. The nitrogen was gone. And with the nitrogen went the last acoustic property of normal air. Sound in helium was a different phenomenon. The speed of sound in helium was roughly three times the speed of sound in air, which meant that the resonant frequencies of the human vocal tract shifted upward by the same factor, which meant that every man in the chamber now sounded like a character in a cartoon.

Sean said something — Kwame did not catch the words — and the sound that came from Sean's mouth was so high-pitched, so removed from the deep Cork baritone that Sean possessed at surface, that Fraser laughed, and Fraser's laugh was itself a helium laugh, a squeaking, chipmunk laugh, and then they were all laughing, six men squeaking and chittering in their steel tube like a nest of bats disturbed by light, and the laughter was genuine but it was also a release, a way of acknowledging that they had crossed a line, that the world of normal sound was above them now and they would not hear their own real voices for twenty-eight days.

The unscrambler helped. The electronic voice unscrambler on the communications system shifted the frequency back down, allowing the topside crew to understand the divers' speech and allowing the divers' outgoing phone calls to sound approximately human. But inside the chamber, there was no unscrambler. Inside the chamber, you heard each other raw — the helium voices, the squeaking, the strange music of men living in an atmosphere that was almost entirely not-air.

You adjusted. You always adjusted. The ear recalibrated after a day or two, and the helium voices became normal, became the default, and when you finally decompressed and heard your own real voice again it was the surface sound that seemed foreign, too deep, too slow, as though you had been living at the correct speed and the world above had been operating in the wrong key all along.

Kwame had called his mother from the chamber once, years ago, during his second rotation. The unscrambler had done its work on the outgoing signal, but his mother, hearing his voice processed and electronically adjusted and transmitted from a pressurised steel chamber in the North Sea to a kitchen in Osu, had said: That is not you. Who is this? And Kwame had said, Mama, it is me, it is Kwame, and she had said: My son does not sound like this. My son's voice is deeper. This is a machine talking. And she had hung up.

She was not entirely wrong. The unscrambler was not perfect. It removed the helium pitch but added an artificial quality, a flatness, a machine-made approximation of a human voice that was close enough to fool most listeners but not close enough to fool a mother who had heard her son's first word and every word after and who carried in her memory the exact timbre of his voice the way a musician carries the memory of a note — not as information but as a physical sensation, a vibration in the chest.

He had not called from the chamber since.

The compression continued. Seventy metres. Eighty. Ninety. The pressure gauge climbed with the steady indifference of a clock. Kwame's headache faded as his sinuses equalised. The temperature stabilised as the cooling system caught up. The chamber settled into its compressed state — not comfortable, exactly, but habitable. Survivable. A place where you could eat and sleep and read and wait, provided you did not think too carefully about the physics, about the fact that the only thing between you and a pressure that would kill you in seconds was the integrity of this steel cylinder and the competence of the people monitoring it.

Sarah Webb's voice came through the intercom every fifteen minutes. Kwame could hear her checking the instruments — the oxygen partial pressure, the CO2 level, the total chamber pressure, the temperature, the humidity. Her voice was the voice of the surface, calm and precise, reading out the numbers that described the conditions of their survival.

Chamber pressure seven-zero metres. PPO2 point-four bar. CO2 point-three per cent. Temperature thirty-one degrees. All parameters normal.

The numbers were their weather. The numbers were their sky. Inside the chamber, there was no sunrise and no sunset, no wind and no rain, no change in the quality of light — the fluorescent tubes blazed constantly, dimmed only during the designated sleep period. The only evidence of the outside world was in the numbers: the oxygen they breathed, the carbon dioxide they exhaled, the pressure that held them at depth, the temperature that told them whether the life support system was winning its endless war against thermodynamics.

Kwame opened his notebook. It was a Moleskine, black, the kind sold in the WHSmith at Aberdeen railway station, and he had filled six of them over the years with writing that he did not call a diary because a diary implied a daily practice and his writing was irregular, triggered not by the passage of time but by the pressure of things unsaid, the way a relief valve opens not on a schedule but when the pressure exceeds the set point.

He wrote: Rotation 42. Blow-down commenced 09:15. Six-man team — Mac, Fraser, Tomasz, Sean, Davy, me. Pipeline repair, manifold inspection, 28 days. Mama's blood pressure medicine changed — Yaw told me last night. Did not ask what the new medicine is. Did not ask if the old medicine was not working. Did not ask the questions a son should ask.

He closed the notebook. He put it under his pillow.

At 120 metres — thirteen atmospheres — the blow-down slowed. Point-seven-five metres per minute now, the compression rate reduced because the body needed more time to absorb the gas at higher pressures, the helium pushing into the tissues like water into a sponge, slow and thorough and irreversible until the decompression began.

Kwame felt the pressure as a fullness, a density, a sense that the air — which was not air — had weight. Breathing required fractionally more effort. Not enough to be laboured, not enough to be a concern, but enough to notice, enough to remind you that each breath was a transaction between your lungs and an atmosphere engineered to sustain you, a gas mix designed by people who understood the partial pressures and the solubility coefficients and the oxygen toxicity limits and who had calculated, with the precision of people whose errors would be fatal, the exact composition that would keep you conscious and functional at the bottom of the pressure curve.

The food came through the medical lock at noon. Insulated containers, sealed against the pressure, passed through the small transfer chamber and retrieved by Fraser, who had drawn galley duty for the first week. Steak pie again — the same steak pie they had eaten in the mess last night, because the vessel's cooks prepared the same food for the divers as for the topside crew, the only difference being that the divers' food was sealed into containers and pressurised and passed through a lock and heated in a hyperbaric microwave and eaten with plastic cutlery at a fold-down table in a steel tube at a pressure that altered the way food tasted, the helium atmosphere stripping flavour the way altitude strips flavour in aircraft cabins, so that everything tasted faintly of metal and cardboard regardless of what it actually was.

Kwame ate. The food was fuel. In the chamber, you did not eat for pleasure. You ate because the body required calories — more calories than at surface, because the pressure and the cold and the physical work of diving demanded energy, three thousand calories a day at minimum, and some divers ate four thousand, the body burning through fuel at a rate that reflected the extraordinary metabolic cost of existing at fifteen atmospheres.

They finished compression at 14:47. One hundred and fifty metres. Fifteen point two atmospheres. The gauge settled. The hiss stopped. The silence that followed was not silence — the chamber was never silent, the ventilation fans humming, the scrubbers cycling, the cooling water circulating — but it was the absence of the compression sound, and in that absence was the knowledge that they were at depth, that the blow-down was complete, that their bodies were now saturated with helium at a pressure equivalent to being beneath 150 metres of water.

They were committed.

Gary Hendricks came on the intercom. Blow-down complete. Storage depth one-five-zero metres. Fifteen point two bar. All parameters nominal. First bell run scheduled for 06:00 tomorrow. Bell team one: MacLeod, Asante, and Fraser. Get some rest.

Mac closed his Tom Clancy novel. He looked at Kwame across the two-metre gap between their bunks and said, in his helium voice, which was absurdly high and which carried nonetheless the cadence and rhythm of his natural speech: Another one, then.

Another one, Kwame said. His own voice came back to him unfamiliar, as it always did in the first hours at depth — a stranger's voice emerging from his own throat, the words correct but the sound wrong, like a letter written in the right words but the wrong hand.

Mac nodded. He rolled over. Within minutes, he was snoring — a helium snore, pitched up to something between a whistle and a whine, the sound of a large Scottish man making the involuntary sounds of sleep in an atmosphere that translated everything into a higher register.

Kwame lay in his bunk. The chamber held them. The pressure held the chamber. The vessel held the system. The sea held the vessel. And somewhere above all of it, above the water and the vessel and the platform and the clouds, there was air — real air, nitrogen-oxygen air, the air of the surface, the air of Aberdeen and Accra and every place where people walked and talked in their natural voices and did not think about partial pressures or decompression schedules or the distance between fifteen atmospheres and one.

He thought about his mother's letters. They would be arriving at Crown Street while he was at depth, dropped through the letterbox by a postman who did not know where they had come from or where the occupant of the flat had gone, accumulating on the floor below the letterbox in a small pile that would grow over the twenty-eight days, each blue aerogramme a week's worth of his mother's observations and concerns and love and the particular gentle authority of a woman who had raised two sons alone after their father died and who had never complained about the difficulty of this except once, in a letter Kwame had received three years ago, in which she had written: The house is quiet. I do not mind quiet. But I mind the kind of quiet that means someone should be here and is not.

He had read that sentence many times. He had not responded to it. He had placed it in the category of things he carried — alongside the weight of the water and the pressure of the gas and the knowledge that his welding, good as it was, was performed in conditions where a single mistake could be fatal — the category of burdens that were part of the job, part of the life, part of the bargain he had made when he left Accra at eighteen with a welding scholarship and a suitcase and his mother's hand on his face at Kotoka Airport, her palm on his cheek, the last physical contact between them for months that became years that became the six years that now stood between him and the house in Osu like a wall he had built one absence at a time.

The chamber hummed. The pressure held. The gauges read 15.2 bar, 0.4 bar PPO2, 0.3% CO2, 29 degrees. The numbers described a habitable world. A world in which six men could live and work and sleep and eat and grow their beards and watch their films and read their books and not die, provided the numbers stayed where they were, provided the systems functioned, provided the woman in the dive control room continued to watch and adjust and maintain and care.

Kwame closed his eyes. Tomorrow the bell would descend. Tomorrow he would go through the trunk and the transfer chamber and into the bell and the bell would drop through the moon pool into the North Sea and he would descend through one hundred and fifty metres of black water to the sea floor, where the pipeline waited with its stress corrosion crack, and he would weld.

That was the structure of his days. That was the architecture of his life. Chamber. Bell. Sea floor. Bell. Chamber. A vertical commute through pressure and darkness, repeated daily for twenty-six days, and at each stage of the journey he was enclosed — by the chamber, by the bell, by the diving helmet, by the water itself — and at no stage was he free, and at no stage was he home, and at no stage did he hear his own voice as it actually sounded, the deep voice his mother would recognise, the voice of the man she had raised, the voice that was, at this moment, locked inside a body saturated with helium at the bottom of the pressure curve in the North Sea, five thousand kilometres from Accra, three hours into a twenty-eight-day dive, with twenty-five days to go before the decompression would begin and the slow return to the surface would commence and the hatch would open and he would step out of the steel and into the air and call himself, provisionally, temporarily, returned.

The lights dimmed. The chamber settled. Six men breathed helium-oxygen in the dark, and the pressure held them the way the ocean holds everything: completely, without judgment, without release.