Two Falcon High School students and a teacher were taken by ambulance to a local hospital Thursday morning after having an allergic reaction to a sulfur compound created in an advanced placement chemistry class, according to Principal Cheryl DeGeorge.
Students were conducting a "standard advanced chemistry lab," she said, when a group of students "inadvertently mixed in an additional chemical."
A reaction to sulfur can cause a rash, shortness of breath and a scratchy throat.
El Paso County's Hazardous Materials Unit investigated and determined the cause of the reaction.
About 125 students were exposed to the experiment and were monitored after the incident, DeGeorge said.
The science room and adjacent rooms were evacuated for the remainder of the school day.
Classes will resume as normal on Friday.