On February 21 2005, a mystery chemical leak at Melbourne Airport forced the eight-hour closure of South Terminal and resulted in 57 airline staff, security staff and passengers being treated by paramedics for nausea, vomiting, dizziness, dehydration and respiratory problems. Forty seven of the victims required hospital treatment.

Air testing initially was undertaken by airport engineers for breathability, by Aviation Rescue and Fire Fighting for flammability and in subsequent hours by Metropolitan Fire Brigade scientists for foreign materials or other agents. None of the testings produced abnormal results and consequently, the cause of the illness was not established.