WHILE TRAMMING IN THE EXPLOSIVE CAR TOT HE AREA TO BE BLASTED, THE EMPLOYEE PULLED UP TO CLOSE TO THE DRILLER'S AND RAN OVER A 1"" AIR HOSE. HE THEN JUMPED OFF THE LOCI AND RAN AROUND IT TO THE AIR HEADER AND INSTEAD OF TURNING OFF THE 1"" VALVE, HE OPENED A 3"" VALVE, WHICH WAS AIMED AT HIS CHEST. THE FORCE OF THE AIR BLEW HIM BACK AGAINST THE LOCI AND ON TO THE TUNNEL INVERT.