EMPLOYEE WAS TAKING SUPPLIES UNDERGROUND IN A UNIHAULER. APPROACHING THE VENTILATION DOORS HE GOT OUT AND OPENED THE 1ST SET OF AIRLOCK DOORS. HE MOVED THE UNIHAULER BETWEEN THE DOORS, GOT OFF TO CLOSE THE OUTBY DOORS. AS HE WAS TURNING TO CLOSE THE RIGHT SIDE DOOR, AN AIR CURRENT CAUGHT THE RIGHT SIDE DOOR CAUSING IT TO SHUT AND CAUGHT HIM BETWEEN THE TWO DOORS