"It's just a recommendation," Leo had argued over the phone. "It says 'Recommended Practice,' not 'Thou Shalt.'"

His thumb hovered over the emergency shutdown button. He looked at the API RP 55 PDF again, still open to Section 5.1.2: Any indication of H₂S above background levels during non-routine events shall be investigated before proceeding.

So here he was, midnight shift, waiting on a service crew to come swap out the old gas detectors. To kill time, he scrolled through the PDF. He had read it a hundred times, but tonight, the words felt heavier. He stopped at Section 4.2: Training. The language was careful, almost gentle. Personnel should be able to recognize the odor of hydrogen sulfide at low concentrations (0.13 ppm)… but must not rely on olfactory senses as the primary warning method due to olfactory fatigue.

For half a second, the number jumped to 6 ppm. Then back to 0.0. Then 0.0 again.

Then it flickered.

Then the number jumped to 12 ppm. Held for three seconds. Then 0.0.

Danny came running back to the control room, face pale. "What the hell, Leo?"

Leo remembered his first day in the field, fifteen years ago. An old hand named Cutter had handed him a half-crushed respirator and said, "If you smell rotten eggs, run upwind. If you stop smelling it, run faster. That means your nose is dead and your lungs are next."

"Smell? Just diesel and my own sweat. Why?"

Leo minimized the PDF and pulled up the well's real-time data. Pressure was normal. H₂S reading was 0.0. Good.