AMERICAN FLT 132 WAS LOADED WITH UNDECLARED & IMPROPERLY MARKED HAZ MTRL (HM) PACKED IN A FIBER DRUM. IT CONTAINED 5 GALOF 50% HYDROGEN PEROXIDE SOLUTION (OXIDIZER) & 25 LBS OF TEXTREAT S-W (CORROSIVE AGENT; SODIUM ORTHOSILICATE-BASED MIX),SHIPPED BY TEXTILE TREATMENTS INTL. THE DRUM WAS LOADED ON ITS SIDE IN THE MIDCARGO (CLASS-D) COMPRT. HM LEAKED DRG FLT,CAUSING HEAT. JUST BFR LNDG, SMOKE ENTERED PAX CABIN. THE CAPT (AWARE OF RPRTD APU FUMES ON A PREV FLT) WAS SKEPTICAL OF RPRTD SMOKE. AFTER LNDG, HE NOTIFIED ATC OF PSBL CARGO COMPRT FIRE & REQUESTED CFR. ACFT WAS EVACUATED ON TWY; 4 F/A,9 PAX, 2 CFR & 3 GND PSNL SUFFERED SMOKE INHALATION, EYE IRRITATION OR MINOR INJURY. INV REVEALED SHIPPER LACKED KNOW- LEDGE ABT RESTRNS & RQRMENTS OF SHIPPING HM; PROC INADQT FOR DETECTING UNDECLARED HM SHIPMENTS. LACK OF HEAT/SMOKE DE- TECTION EQUIP & INSUFFICIENT FLT CREW COMM RESULTED IN DELAY OF DETECTING IN-FLT FIRE & DECLARATION OF EMERGENCY. INADQTDESIGN OF CARGO COMPART & ITS LACK OF FIRE EXT RDCD THE ABILITY TO STOP OR PREVENT SPREAD OF FIRE. (SEE: NTSB/HZM-88/02)