A tanker was unloading anhydrous ammonia at a Tanner Industries distribution facility in Lexington County about 8 a.m. when a hose connecting the truck to a storage tank ruptured, Department of Health and Environmental Control spokesman Thom Berry said.
About 1,800 gallons of the 7,500 gallons on board spilled out before one of the truck's drivers could hit an emergency shut off valve, stopping the spill, Mr. Berry said.
The vast amount of ammonia -- a hazardous chemical typically used in cleaning products -- quickly evaporated, creating a plume of noxious gas that drifted across nearby U.S. Highway 321, Mr. Berry said.
Jacqueline Ginyard, 38, of Wagener, drove into the cloud, tried to get out of her vehicle and was overcome by the fumes, Lexington County Coroner Harry Harman said.
"This material was nearly 100 percent pure ammonia," Mr. Berry said. "It is a strong irritant. It does cause burning of the eyes, throat and lungs."
More than a dozen people in the area received medical attention.
Seven were taken to a hospital in Lexington for treatment of injuries that were not life-threatening, and seven others either declined treatment or were assisted at the scene, Mr. Berry said.
All staffers at the Tanner facility were evacuated.
Officials did not think nearby residents are in danger, although Mr. Berry said several DHEC teams went door-to-door in the predominantly rural area, talking with people about the leak.
Since the ammonia evaporated almost instantly, little cleanup was needed, Mr. Berry said, though some nearby bushes and grass were blackened by the liquid.
A spokesman for Tanner Industries said the Southampton, Pa.-based company would send a team to investigate.
The U.S. Chemical Safety Board is also sending a team of investigators.