A crack in a heat exchange unit led to the evacuation of city employees when carbon monoxide was detected in a city building on Monday, Feb. 1.

The Parks and Recreation and Community Development departments work out of the building, located at 120 So. Sierra Ave., in the building previously owned by Hersheys Chocolate. It was the Hershey Visitors Center until the City of Oakdale purchased it in 2007.

According to Oakdale City Manager Steve Hallam, Danelle Stylos, the city’s community development director, arrived at work at about 7:30 a.m., and soon became lightheaded. One other employee arrived before the Oakdale Fire Department got on scene to test the air in the building.

Fire officials detected high levels of carbon monoxide in the building, and traced the source to the heat exchange unit.

Fire officials determined Stylos should be transported to Oak Valley Hospital after she continued to show signs of ingesting carbon monoxide once outside the building.

Other employees who have worked in the building were instructed to receive medical clearance, as the city did not know how long the heat exchange unit has been malfunctioning.

All employees were back to work Feb. 2.

Although the city renovated the Hersheys Visitor Center to serve as city offices, the heat exchange unit is part of the original infrastructure of the building. The building will remain closed until the heat exchange unit is replaced and the air tested. It is expected to reopen within a couple days, according to Hallam.

Those employees who work out of the building will temporarily relocate to other city offices.

Residents who need to contact Parks and Recreation or Community Development may do so at 845-3571.