Update: Since we published this story yesterday, the Metropolitan Police has reported that a CS canister has been found at Heathrow T4. The supposition by the Metropolitan Police that it was a case of mass hysteria appears to have been inaccurate.
Heathrow’s Terminal 4 was evacuated on September 8 as fire crews were called in to investigate “possible hazardous materials” at the London airport. After a few hours of halted flights and frustrating inconvenience, emergency services declared that no “adverse substance” had been found anywhere in the airport.
People were allowed back into the terminal, and normal service was resumed. In the meantime, however, 21 people were treated at the scene by the London Ambulance Service. So what really happened at Heathrow?
