Numerical Study on the Effect of Atmospheric Wind on the Fire Severity in Informal Settlements with Different Dwellings' Wall Thermal Characteristics

Our plain-English summary of Numerical Study on the Effect of Atmospheric Wind on the Fire Severity in Informal Settlements with Different Dwellings' Wall Thermal Characteristics, by C.K. Lemmertz, M. Beshir, D. Rush, et al (Fire Technology, 2025).

The study

• Authors: C.K. Lemmertz, M. Beshir, D. Rush, F.R. Centeno
• Journal: Fire Technology
• Published: 2025;61(3):1157-1197
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

There is a persistent risk of large-scale fire conflagrations in informal settlements, which can threaten hundreds of people simultaneously. Although the literature implies that wind conditions have a significant impact on these fires, little is known about how wind conditions affect the dynamics and spread of flames in informal settlements. In order to comprehend the impact of wind conditions (speed and direction) on the time to flashover and fire severity in informal settlement dwellings with different wall thermal characteristics, a numerical study was conducted utilizing the Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) code. For six different wind speeds (1 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s and 25 m/s) and two wind directions (side and back wind). Simulations were conducted with full-scale informal settlement dwellings burning wood cribs, analyzing the fuel mass loss rate, hot gas temperature, global equivalence ratio, radiative heat flux outside the door, and time to flashover. In addition, the influence of wall thermal properties was examined for thermally-thin steel-clad and asbestos cement-clad dwellings (thermally-thick). Regardless of wind direction, it was noticed that an increase in wind speed significantly shortened the time required to attain flashover. This was shown to be the result of the wind accelerating the burning rate of the wood cribs and, as a result, the faster temperature rise of the hot gas. Radiative heat fluxes observed outside the door increased with the wind speeds. The direction of the wind had a small effect on the investigated fire characteristics, with the side wind scenarios exhibiting somewhat longer timeframes to flashover. Thermally-thin walled informal settlement dwellings exhibited a greater fire severity, with higher fuel mass loss rates, hot gas layer temperatures, and higher external radiant heat fluxes, as well as shorter timeframes to flashover. These findings indicate that both wind speed and thermal wall characteristics have a substantial impact on the severity of fires in informal settlements and can enhance the risk of fire spread.

© The Author(s) 2023.

In plain English

This was a computer simulation of fire in a single informal settlement dwelling. It did not study asbestos exposure or health. The authors used the Fire Dynamics Simulator, checked against a full-scale experiment, to model a standard-size room with one door and a burning wood crib. They compared 0.5 mm steel sheet walls with 13 mm asbestos cement sheet walls, under six wind speeds from 1 to 25 m/s on the back or side wall. Raising the wind from 1 to 25 m/s shortened the time to flashover by 39.7% to 46.7%, depending on the scenario. Wood burned faster as wind increased. Radiant heat outside the door generally rose too, but in some scenarios leveled off or fell slightly at higher speeds. Asbestos cement dwellings took longer to reach flashover. The steel dwellings reached it on average 29.2% sooner (range 20.6% to 39.6%). Wind direction had a small effect. The authors concluded that wind speed and wall thermal characteristics can contribute to fire severity and may increase fire spread risk. They noted that only one dwelling was modeled.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Numerical (computer simulation) parametric study using the Fire Dynamics Simulator, validated against one full-scale compartment fire experiment
• Who was studied: No people were studied. The authors simulated one full-scale dwelling: an ISO 9705 room (2.4 m by 3.6 m by 2.4 m high) with a 0.8 m by 2 m door, burning a wood crib. There were 24 simulated cases (12 steel-walled, 12 asbestos cement-walled).
• Exposure: The conditions varied were wall material (0.5 mm steel sheets, called thermally-thin, versus 13 mm asbestos cement sheets, called thermally-thick) and atmospheric wind (1, 5, 10, 15, 20 and 25 m/s, blowing on the back wall or the side wall). Asbestos cement appears only as a building material in the fire simulations. No asbestos exposure or health outcome was studied.
• Main results:
  • Across all scenarios, the time to reach flashover fell by between 39.7% and 46.7% when wind speed was raised from 1 m/s to 25 m/s.
  • The fuel mass loss rate (burning rate) of the wood crib rose with wind speed, regardless of wind direction or wall properties.
  • The steel-walled (thermally-thin) dwellings reached flashover sooner than the asbestos cement-walled (thermally-thick) dwellings under the same wind condition. The reduction ranged from 20.6% to 39.6%, with an average of 29.2%.
  • Steel-walled dwellings always had a larger fuel mass loss rate (burning rate) than asbestos cement-walled dwellings under the same wind conditions.
  • Wind direction had a minor effect. Flashover with back wind came on average only 2.1% earlier than with side wind.
  • In the transient results, radiative heat flux measured outside the door increased with wind speed for both wall types.
  • The rise in radiant heat was not uniform. For steel-walled dwellings with back wind, the average post-flashover radiative heat flux rose sharply up to 10 m/s and then rose much less. With side wind it rose up to 15 m/s and then decreased somewhat.
  • Hot gas temperature at the time of flashover was between 552 and 729 degrees Celsius across the scenarios.
  • Average flame lengths outside the door varied between 1.13 m and 2.31 m across the cases.
  • The effects of wind speed were greatest up to winds of 10 to 15 m/s.
• The authors' conclusion: The authors concluded that wind speed and wall thermal characteristics can contribute to the severity of an informal settlement fire and may increase the risk of fire spread.
• Limitations the authors state:
  • Only a single dwelling was modeled. The authors stated that future research should investigate several close dwellings.
  • A traditional mesh sensitivity analysis could not be done because of the domain size and limited computing power.
  • Besides their different thermal properties, the steel and asbestos cement walls also differed in emissivity.
  • Gas analysis was not measured in the experiment used to validate the model.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement.

Related studies

• Polymer-Based Thermal Protective Composites: The Role of Reinforcement and Matrix in Providing Strength and Fire Resistance — M. Meiirbekov, A. Kuandyk, et al. (2025)
• Numerical simulation of heat dissipation characteristics in PWR high-pressure coolant pipes during cold shutdown — F. Tang, W. Wang, et al. (2025)
• Risk assessment of asbestos containing materials in a deteriorated dwelling area using four different methods — Y.L. Zhang, H.S. Byeon, et al. (2021)
• Characteristics of airway obstruction severity in relation to air pollutant in asbestos-exposed chronic obstructive pulmonary disease individuals: A cross-sectional study — M. Yu, X. Lu, et al. (2026)
• Malignant Pleural Mesothelioma: Are There Imaging Characteristics Associated With Different Histologic Subtypes on Computed Tomography? — J.G. Escalon, K.A. Harrington, et al. (2018)
• Difference in carcinogenicities of two different vapor grown carbon fibers with different physicochemical characteristics induced by intratracheal instillation in rats — K. Sato, H. Fukui, et al. (2023)

Browse return to medical research.