TWENTYNINE PALMS, Calif. (AP) — A military hospital on Friday released the last five of 22 Marines accidentally exposed to a fire retardant gas during a training exercise at a Southern California base, a Marine Corps spokesman said.
The Marines were treated for exposure to halon after an extinguishing system accidentally activated in an amphibious assault vehicle during an exercise Thursday at the Marine Corps Air Ground Combat Center in Twentynine Palms.
The five were kept for observation overnight at the base hospital, Capt. Justin Smith said.
Officials were investigating what caused the fire suppression system to go off inside the tank-like amphibious assault vehicle, Smith said. There was no fire or explosion.
Halon gas is widely used in fire extinguisher systems because it is relatively nontoxic and leaves no residue, but it can cause breathing problems at high concentrations. The U.S. banned new production of halon in the 1990s because it can deplete ozone in the atmosphere, but its use is still allowed.
The Marines were from the 2nd Battalion, 3rd Marine Regiment, based in Hawaii and were participating in an integrated training exercise at the Southern California base, according to the Marine Corps.
They were inside an armored vehicle that is used to ferry Marines from ships to shore.
Twentynine Palms, 130 miles east of Los Angeles, is the largest Marine training base in the world. Thousands of Marines take part in live-fire drills in rugged terrain deep in the Mojave desert.
In January, two Marine pilots, Capt. Elizabeth Kealey and 1st Lt. Adam Satterfield, were killed when their helicopter crashed during a training exercise at the base. The cause of the crash is under investigation.