A direct proportionality has been found between the smoke extinction area (SEA) for smoke of room linings and the SEA as measured in the cone calorimeter (ISO5660). The room test scenario (ISO9705) considered was the propane ignition burner at the corner with a 100/300 kW program and the specimen lined on the walls only. The mixing of smoke from propane and lining flames in the hot vitiated ceiling layer and within the exhaust system was modeled by adding contributions from heat release rates of propane and linings separately as a function of time. With overventilation and flaming generally existing in the room, the best correlation was a value of 0.3 for the ratio of lining SEA (= EHC*RSP1 /RHR1) to the peak SEA measured in the cone calorimeter of a horizontal specimen exposed to the flux of 35 kW/m2 during flaming. The test room linings in the order of increasing value of SEA were determined as plywood (including fire-retardant treated (FRT)), lumber, wood composite, and FRT polyurethane foam.