Charleston County detention officers were forced to evacuate the jail's control room Monday morning after the fire suppression system activated during a routine inspection.

The jail on Leeds Avenue in North Charleston immediately went on lockdown. Deputies -- some toting shotguns -- were brought in to create a perimeter around the facility as a precaution. But there was never any real threat of inmates escaping, Chief Deputy Mitch Lucas said.

An employee from the system's vendor was conducting a routine inspection when he accidentally released fire-suppressing chemicals into the Cannon Detention Center control room, where officers monitor nearly 700 cameras and control access to some 200 doors, authorities said.

The four employees inside the room evacuated after the 10:40 a.m. release, leaving the cameras and doors unmanned, Lucas said.

The doors remained locked during the episode, so the 1,400 inmates inside the jail had no way of getting out, he said.

None of the workers suffered ill effects from the release, and no one was injured during the incident, Lucas said. Normal operations resumed about 45 minutes later.

North Charleston firefighters were called in for assistance and found no sign of fire or damage from the release, fire department spokeswoman Bianca Sancic said.

The FM-200 system uses a "clean," nontoxic chemical to put out fires while leaving no damaging residue behind. The FM-200 is a successor to older systems that used halon gas, which is no longer manufactured due to concerns about its effect on the ozone layer.

The incident occurred months after a similar episode resulted in a costly gaffe for the county. In September, an emergency drill ended with a worker mistakenly triggering the release of halon at the county's records center, which is also on Leeds Avenue. The county had to pay nearly $100,000 to refill that system's tanks with 4,500 pounds of halon gas, officials said.

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