WHEN EMPLOYEE CLOSED THE ROOF DOOR ON SECTION 1A ELECTROSTATIC PRECIPITATOR, A CHAIN LINK FELL BETWEEN THE DOOR AND DOOR FRAME, PUTTING THE DOOR IN A BIND. EMPLOYEE STRAINED HIS LEFT SHOULDER PULLING THE DOOR BACK OPEN. HE DID NOT SEE A PHYSICIAN UNTIL 12/18/03. INJURY BECAME REPORTABLE ON 12/23/03 WHEN DOCTOR ADMINISTERED AN INJECTION.