This is the second time this month students of Nelson Hall have been awakened to carbon-monoxide alarms and evacuated.

At 4:30 a.m. on Oct. 17, carbon-monoxide alarms went off, and the DU Department of Campus Safety ordered Nelson residents to evacuate. The Denver Fire Department measured carbon-monoxide levels in the building and determined it was safe for students to re-enter the building 15 minutes after being evacuated.

According to University spokesperson, Kim DeVigil, the Oct. 17 incident was caused by the weather.

"We had a very high wind situation that created kind of an inversion, so the exhaust from the fans were trickling back through," Kim DeVigil said.

DeVigil says the cold temperatures contributed to a similar situation taking place on Friday morning.

Evacuated students were told to go to Nagel Hall, but some huddled together with blankets outside Nelson Hall for more than an hour before seeking shelter elsewhere.

"It was really crazy. We had to get up and get out. It was really early and we all walked to the dorm next door and just waited," Kent Morris said.

Lt. Phil Champagne of the Denver Fire Department says carbon-monoxide readings in the building were around 20 parts per million. He said typically readings need to be around 50 parts per million before people start feeling symptoms of carbon-monoxide poisoning.

Champagne says there were no reports of anyone with symptoms of carbon-monoxide poisoning and no one was taken to the hospital in either incident.

Students tell 9NEWS that they have been told to pack their bags in case the incident happens again.

(KUSA-TV © 2012 Multimedia Holdings Corporation)