An experimental study on the effects of the existence of an adjacent obstruction on informal settlement fire dynamics and spreading

One of the most noticeable characteristics of informal settlements is their high dwelling density. Informal settlements are heavily packed, with small separation distances between dwellings being one of the main parameters responsible for the increased risk of fire spread. However, how the separation distance affects fire dynamics and fire spread mechanisms between buildings is not clear, especially for dwellings built entirely with thermally thin materials, such as corrugated steel sheets. For this reason, reduced scale experiments have been conducted to assess the influence of the presence of an adjacent obstruction and the effects of the separation distance between the fire dwelling and such obstruction on fire dynamics and fire spread in informal settlements. The experiments were conducted with two different setups in a quiescent environment. The first setup consisted of two ¼ scale thermally thin bounded (steel clad) ISO standard rooms (dwellings), and five separation distances were tested (200, 300, 400, 500, and 600 mm). The second setup used the same compartment as the fire dwelling and a wide wall three times wider than the compartment as an obstruction, this wide wall represents a limit wall between properties or a larger dwelling; the same five separation distances were assessed. Heat release rates (HRRs), gas temperatures, radiative heat fluxes (RHFs), and wall temperatures were measured. We found that the wide wall scenarios presented a more severe fire scenario and more potential for fire spread, presenting higher HRR, hot gas temperatures, wall temperature, incident RHF at the adjacent obstruction, and adjacent obstruction wall temperatures. Additionally, lower times to flashover, and consequently earlier external flames were observed, which also contribute to the increased likelihood of fire spread.