Abstract
Aim: The aim of this article is to present the characteristics of various stairwell heat and smoke exhaust ventilation systems.
Introduction: Stairwell smoke exhaust ventilation represents a facultative solution approved by Polish law as an alternative to more effective, but expensive pressure reduction systems. The article concentrates on limits and serious threats associated with unaware use of various configurations of smoke ventilation devices. The analysis involved: natural smoke and heat exhaust ventilation systems, exhaust ventilation systems with powered ventilators (fans) as well as the newest solutions for smoke removal from vertical escape routes with mechanically-aided air supply.
Methodology: All arguments presented in this paper are based on the authors’ many years operational experience. Provided information was confirmed by the results of numerical analyses as well as field research and full-size in-situ fire tests carried out in the presence of the authors. Realisation of the research programme “Bezpieczna ewakuacja” (Safe Evacuation) involved a comparison of, i.a., the operation principles of the stairwell smoke ventilation systems in various conditions of fire development and during dynamically changing stairwell leaktightness (by adjustment of doors position on the floor of fire origin and on the bottom floor as well as after a window break in the test room). The tests were carried out in a real building, characterized by the architecture features representative for the tallest buildings in Poland classified as SW (medium-height), according to [1]. The test stand was equipped with measuring, monitor, control, data collection and archive systems. Together with the field research, the authors performed numerical analyses based on models, validated in the course of hot smoke and fire tests.
Conclusions: All performed tests clearly show that stairwell ventilation systems aided by a mechanical air supply work the most efficiently, but they should be equipped with performance-regulated fans. Natural smoke exhaust systems have the most limitations. They include clear loss of efficiency at low temperatures of combustion gases (in the initial phase of fire development), at disadvantageous difference of temperatures between a stairwell and outside area, and system’s vulnerability to wind influence. The use of powered mechanical ventilators (fans) for exhaust of air and smoke from the building stairwell ought to be considered inappropriate or even dangerous. Presented paper may constitute a useful source of information for everyone who participates in a choice or design of stairwell smoke ventilation systems.
Keywords: stairwell, natural smoke ventialation, mechanical air supply, smoke exhaust fan
Type of article: original scientific article