The Oxygen Lie

The maintenance corridor beneath Sector Nine vibrated like a throat clearing - metal singing underfoot, fans coughing in the walls. Tom walked the narrow service run with his wrist light angled low, the beam catching on frost-like dust where the insulation had flaked years ago. Above him, the dome’s public air carried on in polite silence, filtered and recycled until it felt like a promise. Down here, the promise had a sound: the steady churn of blowers and the soft tick of gauges that never stopped arguing with themselves.

His badge still read “ROUTINE” when he held it near the access plate, and the broadcast loops in his head were fresh enough to taste: outside air toxic, outside air lethal, outside air the reason they were safe. Tom had believed it because the dome kept him breathing, because every morning his bunkmate joked about the weather as if weather could reach them. His shift was simple. Check the pressure seals. Inspect the filter housings. Sign off. Go home.

That was what he wanted - nothing more than to keep the line moving without anyone noticing the way his hands always lingered an extra second on the access latches, like he was listening for a lie in the metal.

The corridor narrowed as it turned under a support rib, and the air grew warmer by degrees. His coveralls stuck faintly at the thigh where sweat had started to bead, and the wrist light threw hard shadows across the mesh grating. Somewhere beyond the next junction, a blower motor changed pitch - just a wobble, then back to normal. Tom slowed, letting the sound settle in his bones. He didn’t have to open anything yet; the system would log his presence if he triggered the wrong panel, and supervisors didn’t like log spikes.

“Halden,” a voice said behind him, flat through the corridor speakers, as if it was coming from the pipes themselves. “You’re on schedule.”

Tom didn’t turn right away. He watched his own breath fog the edge of his light for half a second before the sensor fan pulled it away. “Yeah,” he said. “Just doing the usual checks.”

A pause, then the speaker crackled again. “Keep it routine. We’ve had enough anomalies. Sector Nine’s air is under review.”

Tom felt the word under like a pressure change. Anomalies meant delays, and delays meant people asking why you were in the wrong place at the wrong time. He forced his shoulders to relax. “Understood.”

He moved to the next access point marked with faded stencil: FILTER HOUSING / BAY 3. The label was older than the current paint, but the numbering was crisp. He keyed his wrist against the panel and waited for the click that meant permission. The latch released with a reluctant thunk, and the corridor’s hum shifted - less muffled, more direct. Cold air seeped from the seam around the door, sharp enough to sting his nostrils.

A maintenance sign blinked on the inner panel: BAY 3 ACTIVE. That should have meant the housing was running normally. Tom leaned in anyway, bringing his light across the housing’s inspection window. The glass was filmed with grime, but the internal indicator strip should have been a steady green.

It wasn’t.

The strip pulsed a dull amber, then went dark for a beat before snapping back to amber again, like a tired heartbeat. Tom listened. The fans sounded fine, but the rhythm had a hitch, a stutter in the airflow that made the hairs on his forearm lift under the fabric. He rested two gloved fingers on the window frame and felt a vibration that didn’t match the corridor’s baseline.

“Halden?” came the supervisor’s voice again, closer this time. Tom realized with a jolt that someone had followed his route without needing to announce it. He turned and saw Jaro at the far end of the corridor, tall and broad-shouldered in the grey maintenance coat with the Sector Nine patch. Two guards stood behind him, their visors reflecting the pale wrist light as if the corridor itself were watching.

Jaro’s expression didn’t change, but his eyes tracked the amber pulse. “You’re early.”

“I’m not,” Tom said, and hated how defensive it sounded. “The system’s - it’s showing active fault.”

Jaro stepped closer without rushing. His boots made a different sound than Tom’s - heavier, confident. “Faults happen. You log it, you seal it, you move on. That’s routine.”

Tom swallowed. The corridor air was still cold at the seam, still sharp. He could smell something he couldn’t name - metallic and dry, like dust kicked up from a long-closed room. “It’s pulsing,” he said. “BAY 3 isn’t stable.”

One of the guards shifted their stance, a soft scrape of polymer on grating. “Sabotage risk,” the guard said. His tone matched the corridor speakers - too practiced to be spontaneous. “We’re watching.”

Tom stared at the amber strip until his eyes tried to make it into something else. The outside was toxic, the dome was safe. That was the story everyone repeated, the story that kept the public calm and the dome’s authority unchallenged....