The Pentagon was placed on a partial lockdown Thursday morning after building sensors detected an air quality issue, prompting a hazardous-materials response from local emergency services. The incident affected approximately half of the five-story building, which houses more than 20,000 Department of Defense employees.
Pentagon spokesperson Sean Parnell said in a statement that the building’s systems detected “an air quality issue necessitating precautionary measures until we determine its significance.” He said the department is “executing standard protection protocols, including a shelter-in-place order for the affected area.”
The Arlington Fire Department announced in a social-media post that a hazardous-materials team was responding to the situation. A fire department official said the department was assisting the Pentagon with the incident. Police inside the building were seen wearing gas masks and full chemical protective gear, according to US media reports.
The lockdown covered four corridors on three floors, according to a Defense Department official cited by The Wall Street Journal. The Pentagon’s main building has five floors arranged in five concentric rings, and the affected area represented roughly half of the total floor space.
Officials did not immediately disclose the substance or the source of the air quality issue. Parnell described the response as “precautionary measures” that would remain in effect until authorities determine the significance of the incident.
The Pentagon, located in Arlington, Virginia, serves as the headquarters of the US Department of Defense. More than 20,000 government employees work in the building. The incident came less than three months after a chemical smell halted flights at four Washington-area airports for over an hour in March, an incident authorities later said was not suspicious.
Emergency response teams remained on the scene Thursday as the investigation into the cause of the air quality issue continued.