A failure in an HVAC unit on the roof caused Northern Lehigh High School to be evacuated Monday morning.

The incident occurred around 10 a.m., according to Superintendent Matthew Link, who said that students and staff exited the building, and a short time later, entered the middle school auditorium.

“The cause of the fire alarm was due to a failure in an HVAC unit on the roof that sent smoke and an odor into sections of the building,” Link said. “The evacuation went as planned, and at no time was anyone in danger.”

Link said that the Slatington, Walnutport and Neffs fire departments, along with Slatington Police Department, and Northern Valley Ambulance, responded to the alarm.

“First-responders and our internal response team determined the cause of the smoke, isolated it and then began to exhaust the building,” he said. “After the odor was mitigated and air quality checks were conducted throughout the building, the fire departments notified administration that the students and staff could return to the building at approximately 12 p.m.”

Link said a modified schedule for classes and lunches was implemented for the remainder of the day.

“I would like to thank all of the first-responders for their immediate response and coordinated efforts,” he said.