Brussels gas works set " ablaze " in aerial bomb and gas attack . Men , women and children lay prone on the Brussels pavements when a mock aerial bomb and gas attack was made on the city to test the defences . The citizens co operated with the military authorities to make the attack as realistic as possible . Gas masked Red Cross men rushed " victims " to first aid centres , and fire fighters wearing gas masks concentrated their efforts on buildings set alight by the " bombs " . Gas masked firemen pouring water on the " blazing " Brussels gas works . 6 September 1934