Cris Abraham, 36, was among four people inside a utility room on Monday when carbon dioxide was suddenly released from the fire suppression system, displacing oxygen in the room.
The odorless gas caused the husband and father of two to go into cardiac arrest. Firefighters arrived wearing protective gear, got him to safety and performed CPR. He was hospitalized in critical condition.
Three other people who had been in the room at the time were able to evacuate safely.
It's not clear yet what triggered the discharge of carbon dioxide, as there were no indications of a fire.
Cal OSHA is investigating.
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