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The results of large scale experiments on the prevention of smoke travel along covered pedestrian malls by natural venting are presented and discussed. Fires of 0.6, 1.1 or 3.2 MW output were set in a 'shop' giving on to a covered 'mall' or arcade about 17 m long, 6 m wide and 3 m high. Measurements of the temperature, layer depth, rate of flow and opacity of the smoke-laden hot gases were made in the mall with and without venting and with and without a ceiling screen in the mall and a fascia board in the front of the shop. The experiments show that the spread of smoke along the mall can be prevented by the combined action of a venting system and roof screens - neither being effective alone. Because substantial quantities of air mix with the smoke layer as it passes along the mall the venting system should have a larger capacity than would be required for fires in simple single-storey buildings. A number of small vents spaced well apart over the whole ceiling are likely to be much more effective than a single large vent of the same nominal venting capability.