The Memorial Union was closed Tuesday for the second time this school year due to a fire alarm, but this time it was reopened after just 20 minutes.
The building was evacuated when the fire alarm went off around 10:30 a.m., ASU spokesperson Leah Hardesty said.
An employee triggered the alarm by accidentally setting off a fire extinguisher in an internal stairwell, Hardesty said.
"That created yellow dust in the air, and the dust is what caused the fire alarm to go off in the stairwell," she said, and the incident appeared to be accidental.
Students were kept outside of the building for about 20 minutes while University staff cleaned up the dust, Hardesty said.
The Tempe Fire Department was not dispatched to the scene, said Mike Reichling, a fire department spokesman.
