University officials discovered Monday what is behind the natural-gas smell pervading southeast-campus buildings.

A professor in Kolthoff Hall has been dumping a chemical known as mercaptan down the drain, producing a rancorous smell in many University buildings along East River Road and provoking several evacuations during the last week.

Mercaptan is a nontoxic chemical added to natural gas to give it a powerful, alerting smell.

“There is no life threat, no safety threat, no health threat,” said Judson Freed, University emergency management director. “You might feel sick because it’s a bad smell, but it’s not going to make you physically sick.”

Students and staff at Boynton Health Service and the Mayo Building, who were unaware of the smell’s source, decided to evacuate the buildings Friday.

“We ran every test in the book (this weekend),” Freed said.

Since University officials determined the smell was nontoxic, numerous agencies – including the University’s environmental health and safety department – have been working tirelessly to discover the smell’s origin, Freed said.

University police received several complaints Monday afternoon about the odor’s reoccurrence but did not know the cause until that night.

“On Friday we knew what it wasn’t; today we knew what it was,” Freed said.

Freed said he is investigating whether the professor dumping the chemical is following the proper environmental precautions. He said the professor told University officials he had been conducting the experiment for a month before the smell seeped into campus buildings through sewers. Freed said he did not know the professor’s name.

“If it is not in violation of some procedure, then the procedure itself needs to be changed,” he said. “It’s not going to happen again, we hope.”