Department of Environmental Protection employees were evacuated from a building due to high levels of chlorinated vapors.

The building is located on the Jerome Park Reservoir on Goulden Avenue. Officials say too much chlorine was added to water in a holding tank. They say when workers locked up Thursday night, there was no ventilation in the building.

Fire officials say when workers arrived Friday morning, monitors alerted them of the elevated chlorine levels in the air.

Four employees were treated on the scene. Workers were allowed back in the building later in the day. None of the other surrounding buildings were affected.

DEP officials say it is standard procedure to add chlorine to water pumped into the reservoir.