Charleston County detention officers were forced to evacuate the jail’s control room this morning after the fire suppression system activated during routine maintenance.

The jail immediately went on lockdown and deputies — some toting shotguns — were brought in to create a perimeter around the facility. But there was never any real threat of inmates escaping, Chief Deputy Mitch Lucas said.

Workers had shut off part of the system while performing routine maintenance. Something, however, caused the system to release fire-suppressing chemicals into the jail’s control room, where officers monitor nearly 700 cameras and control access to some 200 doors, Lucas said.

The four employees inside the room evacuated after the 10:40 a.m. chemical release, leaving the cameras and doors unstaffed, Lucas said. The doors remained locked during the episode, so the 1,400 inmates inside the detention center had no way of getting out, he said.

None of the workers suffered any ill effects from the release, and no one was injured during the incident, Lucas said.

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,” non-toxic 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.

It’s unclear how much, if anything, Monday’s release will cost the county. Officials were trying to determine exactly what set off the system and who is responsible, Lucas said.

In September, an emergency drill that ended with a worker mistakenly triggering the release of halon at the county’s Leeds Avenue records center proved a costly gaffe. The county had to pay nearly $100,000 to refill that system’s tanks with 4,500 pounds of halon gas, officials said.