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How to Protect Staircases in Case of Fire in Mid-Rise Buildings.Real Scale Fire Tests

Purpose: The aim of the analysis was to investigate how smoke would spread in the building in the case of fire, and how to protect staircases without a pressure differential system (PDS). It was assumed that a ventilation system should: – prevent the staircase against complete smokiness. The part of the staircase located below the level covered by the fire should be smoke-free to the extent allowing the evacuation of people from the fire compartments; – remove smoke from the staircase as fast as possible to prevent a significant increase in the level of pressure in the staircase. Project and methods: Research was conducted in a full-scale 9-storey building. Three real fires were simulated. Typical apartment furnishings were used in the fires. A smoke ventilation system was installed in the staircase with variable make-up air supply. Tests were carried out for the following configurations of smoke ventilation systems: – natural smoke exhaust with natural/gravitational make-up air; – natural smoke exhaust with a mechanical (fixed volume of 14000 m3/h) make-up air inlet; – natural smoke exhaust with a variable mechanical make-up air inlet. The position of the door between the staircase and the apartment was used as an additional variable. The measurements included temperature, light transmittance in the staircase, pressure difference between the staircase and the external environment, and the flow of the air and smoke through the smoke damper. Results: The results of the research show that the system of gravitational smoke ventilation is susceptible to ambient conditions such as temperature. In some tests, it was observed that smoke could descend below the storey covered by the fire. The conducted research helped determine the best way to reduce the amount of smoke in the staircase. The use of mechanical air supply in the smoke ventilation system facilitated fast smoke removal from the staircase, and the proper air and smoke flow direction (from the test room to smoke exhaust devices). The use of mechanical make-up air supply in the smoke ventilation system prevented the smoke from descending below the storey covered by the fire, so that the staircase on the floor covered by the fire could remain free from smoke in the lower part, providing a way of escape from the level covered by the fire. Conclusions: The conducted tests have revealed that the best solution to protect staircases without PDSs is to use a smoke ventilation system comprising a smoke vent mounted at the top and mechanically adjusted make-up air supply on the ground level.