A janitor poured excess chlorine into what he thought was an empty bottle stored in the South Visitors Center on Temple Square. However, the bottle had just trace amounts of the sulfur left in it, Asay said.
The mixture formed the thionyl chloride, which quickly spread through the building via the air vents, according to those inside the building at the time.
Close to 50 people were evacuated from the building and evaluated by paramedics at the scene. Ten people, including the janitor, were taken to the hospital for further treatment, Asay said.
Susan Lowe was in the building at the time. She said her throat felt scratchy and irritated. She said firefighters told her that for most people, breathing fresh air should take care of the symptoms.
Two hazmat teams from the fire department responded to the 11:30 a.m. incident, which closed Temple Square until about 1 p.m. Temple Square is owned by The Church of Jesus Christ of Latter-day Saints,
It also closed down South Temple and TRAX between the Gallivan Plaza and Arena stations during that time.
The South Visitors Center was reopened by 2:30 p.m.
David Gillette, the Temple Square mission president, was inside the building when he began to smell a strong scent of chlorine. He and his wife, Doris, began to look for the source of the smell.
Several female missionaries who serve at Temple Square began coming out of various rooms to discover what was going on as well.
They had planned to wait it out, but then the fire alarms went off, Doris Gillette said.
They evacuated the building and waited for authorities.
"It's not every day they evacuate Temple Square," David Gillette said.
Tribune reporter Jim Dalrymple II contributed to this story.
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