A 59-year-old civilian contract worker lost consciousness Thursday after being exposed to carbon dioxide from a fire suppression system on a Coast Guard vessel, the city Emergency Services Department said.

The incident happened at about 11:30 a.m. on the Coast Guard cutter Kukui, docked at Sand Island.

The Kukui’s commanding officer, Lt. Cmdr. Steven Ramassini, said the worker was in the stern thruster space, which is a below-deck compartment at the waterline, and had been clearing the way for work on a generator.

That’s when the fire suppression system was accidentally activated, audible and visual alarms went off and carbon dioxide was released.

Other civilian and Coast Guard workers were also in the space, but the affected worker was in the lowest point and did not make it out, Ramassini said.

He lost consciousness and collapsed, but revived on his own after the Coast Guard fire team on board brought him onto the deck, Ramassini said.