DUST SYSTEM LEADMAN WAS RESPONDING TO A LOUD NOISE FROM THE NORTH BAGHOUSE, HE THOUGHT WAS A FAN GOING BAD. HE SLIPPED GOING UP THE BAGHOUSE STAIRWAY AND FELL INTO THE STAIRWAY HADRAIL CAUSING AN INJURY TO HIS RIGHT CHEST/ RIB REGION. HE CONTINUED WORKING UNTIL 4-24-03 AND SOUGHT MEDICAL TREATMENT RESULTING IN RESTRICTED DUTY BEGINNING MONDAY 4-28-03.