A freon leak inside the air traffic control tower at the Burlington International Airport caused a brief evacuation Friday morning.

During the 30 minutes the tower was unmanned, the Federal Aviation Administration's Boston Air Route Traffic Control Center took over directing the airspace, FAA spokeswoman Arlene Salac told Seven Days.

A fire alarm signal around 8:30 a.m. prompted a response by the Vermont Air National Guard's on-site 158th CEF/Fire & Emergency Services and the South Burlington Fire Department. The tower was cleared as firefighters searched for what triggered the alarm, which turned out to be a "very minor refrigerant condition involving the air-conditioning system in an isolated part of the building," South Burlington fire Capt. Sacha LaScala said.

The building was aired out, and no injuries were reported, said Lascala. Freon can be "slightly irritating but dissipates quickly," he added.

Dick Mills, who witnessed the incident from the roof of the airport parking garage, said two United Airlines planes landed while the tower was evacuated. A group of F-16s that were preparing to take off before the evacuation had to wait until personnel returned to the tower, he said.

"It's funny, I thought the F-16s don't wait for anybody but I guess that's not true!" Mills joked. 

No commercial jets were delayed, but two smaller planes were forced to wait to take off, as were the F-16s, said Gene Richards, the airport's director of aviation.