A total of 26 people were treated at the airport after suffering from breathing difficulties and two were taken to hospital, the London Ambulance Service said. All evacuated to the tarmac.”

LorcanJPT ‏London City Airport has been evacuated due to a fire #London

A spokeswoman for London Fire Brigade said three fire engines had been sent to the scene. "Two complete sweeps of the airport building were carried out jointly by firefighters and police officers both wearing protective equipment," the London Fire Brigade said in a statement. He added: “No elevated readings were found and the building was ventilated, searched and declared safe.”

Medics trained to treat people in hazardous situations also attended the scene. The airport was reopened shortly after being declared safe at around 7pm.
Authorities evacuate London City Airport after a chemical incident, but, after some remediation, police later declare the airport safe.