<p> It is known that a flat wooden wall does not sustain flame spread without external radiation. On the other hand, wooden louvers are likely to sustain flame spread, as heat flux from facing blade as well as flame accelerates burning. This study addressed burning characteristics of wooden vertical louvers and fire controlling measures through reduced- and full-scale experiments.</p><p> To figure out the dimensional relationship that sustains flame spread, reduced-scale experiments were carried out. Wooden louvers were simplified as MDF panels facing each other, and backed by steel channels. Blades were 54 or 112mm deep and 1,700mm high. For Each depth, critical pitch that sustains flame spread was evaluated. Flame sources of 12.8kW/m was placed at the bottom of both panels to ignite them. Flame height, temperature and heat flux were observed during the experiment. After screening some dimensions from the above, full scale experiments were also carried out to reproduce the fire phase from burning of small furniture. The specimen was 500mm wide and 3,400mm high. This time, all blades were 58mm deep and 35mm thick, and three louver walls differ in pitch were burnt; 48, 90, 215mm, respectively. All louvers were directly backed by noncombustible wall (12mm thick calcium silicate board). Sidewalls were attached to both sides of the specimen to avoid horizontal transfer of gas and heat. Heat release of the flame source was 200kW, approximately representing a burning of chairs. During the experiment, temperature and heat release were measured. Using the same apparatus, experiments on eaves' effect were also carried out. This time, the pitch of the louvers was also fixed (48mm) and four types differ in presence of eaves and the backing wall were considered.</p><p> From the reduced-scale experiments, it was proved that flame spread is sustained when the pitch is less than 72mm for 112mm deep blades. Sustained flame spread was not observed with 96mm pitch, but the maximum flame height reached approximately six times higher than that of source flame. Heat flux distributions within these louvers are significantly higher than those within a flat wall, and it is also estimated that their differences correspond to radiative heat flux values from facing blade, in the case of louvers 110mm deep. Flame spread becomes relatively inactive when their dimensions are similarly reduced. Full-scale experiment qualitatively agreed with reduced-scale tests, but flame spread rate became approximately 8.5 times faster. In louvers whose pitch is 48mm, high flame spread rate was sustained till the top of the apparatus, and eaves 200mm in depth effectively suppressed flame spread. This effect was higher in louvers without a backing wall.</p><p> Summary and conclusion of this study are as follows:</p><p> 1) sustained flame spread occurs when the pitch is less than 72mm for approximately 112mm in depth</p><p> 2) sustained flame spread do not occur when the pitch is around 96mm for 112mm in depth, yet burns six times higher than the source</p><p> 3) Heat flux distributions within louvers 110mm deep are practically predictable by taking radiative heat flux into account</p><p> 4) flame spread becomes relatively inactive when the dimensions of the louvers are similarly reduced</p><p> 5) eaves are more effective when attached to louvers without backing wall, as their Coanda effect is less than that of solid wall.</p>