Staff at the US Department of Agriculture's (USDA) top research centre have complained to federal regulators about hazards in the site's ventilation system, four months after an initial federal complaint raising other workplace safety concerns, according to a copy of the latest complaint seen by Reuters.

In May, staff at the Beltsville Agricultural Research Center in Beltsville, Maryland, filed a complaint with the US Office of the Special Counsel (OSC), which protects federal whistleblowers, alleging mismanagement and unsafe work conditions including poor lab ventilation, broken fire alarms and wild temperature swings.

After Reuters exclusively reported the complaint, USDA closed one major research building at the site for repairs. In June, the OSC ordered USDA to investigate the workers' claims.

The new complaint sent Friday to the Occupational Safety and Health Administration (OSHA) alleged that the facility's chillers, which are part of temperature regulation systems, have not received maintenance in more than three years. Maintenance tasks should be performed on a schedule ranging from daily to annually, the complaint said.

According to the Centers for Disease Control and Prevention, chiller maintenance is necessary to protect staff and community members from Legionella, a bacteria that can cause the lung infection Legionnaire's disease.

The OSHA complaint also alleges that most of the dozens of buildings on BARC's nearly 7,000-acre campus have not had potable water since the end of 2018 and that several buildings have "unknown substances growing out of ventilation systems."

"Our employees' health and well-being is our top priority," said a spokesperson for the USDA's Agricultural Research Service, which oversees BARC. "USDA continues to investigate these allegations while carrying out its work to modernize this facility and address employees' concerns."

BARC staff conduct research on climate change, invasive pests, crop yields and more.