Carbon monoxide detectors installed only three weeks ago alerted the Watertown Department of Public Works to unsafe levels of the deadly gas in the basement of the department’s Orchard Street headquarters.

Two women were examined by paramedics and the building was closed for a day. Neither person was taken to the hospital, said Gerald Mee, superintendent of the DPW.

The carbon monoxide alarm went off Monday and the Watertown Fire Department investigated. “Extremely high” levels of the potentially deadly gas were found in the basement, according to Mee, and he decided to close the building.

Sometimes called the “invisible killer,” carbon monoxide can build up inside buildings that use fossil fuels such as oil and natural gas for heat. resulting in dizziness, headache, fatigue and, in some cases, death.

The company that services the burner in the building’s basement found that worn-out paper gaskets had caused the leak, Mee said.

Mee credited several DPW workers who had requested carbon monoxide alarms. The alarms were installed three weeks ago, he said. State law requires the detectors in residential properties.

“Thank God we had them,” Mee said.

Mee installed further carbon monoxide alarms on Monday and, after several hours of monitoring on Tuesday, reopened the building Tuesday at noon.