The Pentagon places part of its building under a shelter-in-place order after internal safety systems detect an “air quality issue.” Multiple outlets report that the response includes emergency crews and hazmat teams arriving at the Defense Department headquarters in Arlington, Virginia, after officials say precautionary measures are needed while they determine the significance of the alert. Some reports describe evacuations and floors being locked down, along with responders wearing protective gear and gas masks as they investigate. CBS News and others cite information from the Arlington County fire department, including social media posts indicating the Pentagon is investigating a possible hazmat situation related to air quality monitoring. The Pentagon’s spokesperson characterizes the action as preventive, saying the building has systems designed to ensure safety and that the detected issue triggers precautionary steps until officials assess it. The Independent later reports that the lockdown is lifted after the investigation, though the outlets do not provide detailed findings on the cause in the information provided. Overall, sources agree that the incident is triggered by an internal air-quality detection and leads to an emergency hazmat response before the situation is resolved.