Hitchner Hall reopened at 2:15 p.m., Feb. 21 after a small chemical reaction in a third-floor hallway caused the building to be evacuated midday.
No injuries were reported. As a precaution, four building occupants were sent to Cutler Health Center for observation.
A laboratory manager was attempting to neutralize chlorine tablets in a five-gallon bucket for disposal when the reaction occurred. The chlorine tablets are used for disinfecting laboratories.
The lab manager added sodium bisulfate, followed by water. The chemicals reacted and offed gas.
The lab manager put the lid on the bucket, pulled the fire alarm and called the University of Maine Police Department, which evacuated building.
An estimated 150 people were in the building when the incident occurred.
The Orono-Old Town Emergency Response Team has verified that the chemical reaction was contained in the bucket and there were no further chemical reactions or residual in the building. The hazmat unit placed the bucket in a separate overpack container and removed it from the building.