Four UT students were taken to UT Medical Center Tuesday after their experiment in the Science and Engineering Research Facility exploded.

Capt. D.J. Corcoran of the Knoxville Fire Department said the small explosions caused a two-hour evacuation of the building.

The transported students were not listed as injured in the explosion, but were taken to the hospital as a precautionary measure.

“They’re not having any symptoms, but they went ahead and transported them just to check them out,” Corcoran said.

The boron trichloride gas was in a small, 20-ounce glass tube that exploded after being heated for an experiment.

"Most of the gas, the trichloride, burned up with the flame," Corcoran said. "What that turns into at that point is HCl (hydrogen chloride), which is a chloride, and so we don't really know how much exposure there was."

Both boron trichloride and hydrogen chloride can be toxic and react violently when exposed to air and water.

However, BCl3 is also four times heavier than air, making it possible that contamination was lower to the ground.

“They both pose a respiratory threat,” Corcoran said. “I would say that boron trichloride is probably more dangerous than the other because it’s a corrosive. And it has a violent reaction to moisture and with your lungs being moist inside, it could have a more violent reaction in there.”

Kenna Rewcastle, junior in ecotoxicology and environmental Conservation, said she was on the 7th floor of the building when a fire alarm was pulled and she was told to evacuate.

“There was a policeman kind of ushering everybody out," Rewcastle said. "Because it wasn’t an immediate reaction, it wasn’t a fire that made the fire alarm go off. They called the hazardous material unit and then pulled the fire alarms.”

The hazardous materials unit performed a final check of the building, sweeping through with pH detectors to test for any sign of the chemical before letting students back in.

The team summarized that with the fans and air conditioning still running in the building, the chemicals dissipated naturally into the atmosphere.