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  • 51.
    Sjöström, Johan
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Nytt analysinstrument för termiska egenskaper2011In: Brandposten, no 44, p. 17-Article in journal (Other (popular science, discussion, etc.))
  • 52.
    Sjöström, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Systematisk diskrepans avskogsbrandsrisk baserat påtidsupplösning: Uppskattning av effekter samt förslag tillkorrigering2021Report (Other academic)
    Download full text (pdf)
    rapport
  • 53.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Amon, Francine
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Forest fires in Sweden - Spatial, temporal and climatic patterns2016In: Book of Abstracts Nordic Fire & Safety Days 2016, 2016, p. 32-Conference paper (Other academic)
  • 54.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Amon, Francine K.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Appel, Glenn
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Persson, Henry
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Thermal exposure from large scale ethanol fuel pool fires2015In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 78, p. 229-237Article in journal (Refereed)
    Abstract [en]

    The growing use of ethanol as fuel for combustion engines has dramatically increased the need for large scale storage of ethanol in tanks. There are new risks related to fires in storage tanks having larger volumes. Very little experimental data exist to support risk assessments regarding emitted radiation and burning rate for large pool fires. Experience from small scale tests show that the exposure to nearby surroundings is less for alcohols than for hydrocarbon fuels like gasoline and these results are often extrapolated to fires of large sizes. This paper describes the results of two pool fires conducted within the frame of the ETANKFIRE project, one with 97% ethanol and 3% gasoline and the other with 85% ethanol and 15% gasoline, both with a surface area of 254 m2. The results show, contrary to experience from small scale pool fires, that the exposure to nearby surroundings is much larger for ethanol-rich fuels compared to the calculated radiative heat flux from a pure gasoline fire of same fuel area.

  • 55.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Anderson, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Kahl, Fredrik
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Boström, Lars
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Hallberg, Emil
    RISE Research Institutes of Sweden.
    Large scale exposure of fires to facade - Initial testing of proposed European method2021Report (Other academic)
    Abstract [en]

    This report describes a series of tests of the new proposed method for assessing the performance of façades when exposed to flashover fires. The tests consider the large fire exposure and consists of the 8.5 meter high incombustible walls placed in a 90° angle towards each other. The report assesses reproducibility and the effect of moisture content, stick size, wind and depth of the combustion chamber.The data from the report will be publicly available at the project website for further use and scrutiny. https://www.ri.se/en/what-we-do/projects/finalisation-of-the-european-approach-to-assess-the-fire-performance-of-facades 

    Download full text (pdf)
    Report
  • 56.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Andersson, Petra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Sveriges tekniska forskningsinstitut / Brandteknik, forskning (BRf ).
    Brandrisker vid tankstationer för flytande naturgas2014In: Brandposten, no 50, p. 14-15Article in journal (Other (popular science, discussion, etc.))
  • 57.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Andersson, Petra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Sveriges tekniska forskningsinstitut / Brandteknik, forskning (BRf ).
    Thermal exposure from burning leaks on LNG hoses: experimental results2013Report (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 58.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Blomqvist, Per
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Sveriges tekniska forskningsinstitut / Brandteknik, forskning (BRf ).
    Direct measurements of thermal properties of wood pellets: elevated temperatures, fine fractions and moisture content2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 134, no Oct, p. 460-466Article in journal (Refereed)
    Abstract [en]

    The self-heating propensity of biomass fuels is a major challenge to the large scale handling of e.g. wood pellets. The insulating properties in combination with exothermal processes sometimes lead to fires when larger volumes of wood pellets are stored. Recently, the thermal conductivity and specific heat of wood pellets have been investigated (Gou et al., 2013) through back-calculations of transient temperatures in wood bulk storage. Such properties are important in order to make simulations and predictions about safe storage and use. However, little information is available about the temperature dependence of these properties as well as the bulk properties of broken pellets, which is abundant in critical parts of a storage facility. In this study we show that the specific heat and thermal conductivity of wood pellets can be directly measured using the Transient Plane Source technique. We present data between 22 and 120 °C for bulk wood pelletsand investigate the change in conductivity for fine particle bulk material. In addition, we investigate the possibility of measuring on individual pellets while studying the moisture contentdependence.

  • 59.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Brandon, Daniel
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Temple, Alastair
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Anderson, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    McNamee, Robert
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    External fire plumes from mass timber compartment fires—Comparison to test methods for regulatory compliance of façades2023In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 47, p. 433-Article in journal (Refereed)
    Abstract [en]

    Post-flashover fires inherently lead to external fire plumes, constituting a hazard for rapid fire spread over façades. As multi-storey mass timber buildings with internal visible timber surfaces become more common, there are concerns that such buildings would produce larger external plumes and hazards (assuming all other parameters equal). The literature reveals only indications of this, and how the actual exposure relates to different test methods for assessment is unknown. Here we utilise a series of full-scale mass timber compartment tests to quantify the exposure to the external façade. An incombustible external façade is instrumented with gauges at positions corresponding to reference data from several different assessment methods. The results show that there is an increase in plume duration, height, and temperatures when increasing the areas of exposed timber, but that this increase is less for normal- to large-opening compartments, than was previously seen in small-opening compartments. Also, normal variations in external wind speed have a larger influence on plume heights than the effect of doubling exposed timber surfaces. Test methods used for regulatory compliance differ significantly not only in exposure but also in pass/fail criteria. The proposed European large exposure method and the BS8414 method exhibit exposures on par with the severe end of what could be expected from mass timber compartments, whereas methods like SP Fire 105 and Lepir II produce significantly less severe plumes. However, the safety level is always a combination of exposure and assessment criteria. This data can help justify assessment criteria from a performance perspective. © 2023 The Authors. 

  • 60.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Brandon, Daniel
    Temple, Alastair
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Hallberg, Emil
    RISE Research Institutes of Sweden.
    Kahl, Fredrik
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Exposure from mass timber compartment fires to facades2021Report (Other academic)
    Abstract [en]

    Different countries world-wide have different legislation concerning the performance of facades exposed to fire and often significantly different ways to assess this performance. Although it is recognized that standard façade fire testing aims to distinguish façade systems that limit fire spread to an acceptable level from systems that do not, it has historically been considered important that the fire exposure of such tests is representative for real fires.

    In this study five real scale compartment fire tests, constructed of Cross Laminated Timber and Glued laminated timber were performed with instrumentation on a façade extension above the ventilation openings, providing a means to compare façade performance tests against the exposure generated by realistic compartment fires. The fuel load and openings of four of these tests were determined from a statistical analysis to represent severe fire exposure within a realistic range. Of these tests the surface areas of exposed Cross Laminated Timber and Glued Laminated Timber were varied, allowing an assessment of the influence having internal areas of exposed timber surfaces on the façade fire exposure.

    For these tests, an increase of roughly 40 m2 exposed surface area (from ~54 to ~94 m2 or from 113 % to 196 % of the floor area) resulted in a temperature increase of roughly 100 to 130 °C at the façade at all heights up to 3.5 m above the opening. Additionally, an increased fire plume height of 0 to 1 m was observed. The most significant effect of increased exposed areas was a prolonged duration of the flashover phase.

    The British BS 8414 standard façade fire tests and the recently proposed European façade fire test have been identified to be the most representative for the tested residential fire scenarios in terms of façade fire exposure. Temperature measurements of the North American methods (NFPA 285 and CAN/ULC-S134) are towards the end of the tests also close to the those of the compartment tests. The Swedish SP Fire 105 test imposes the lowest exposure for a relatively short duration to the façade. It should, however, be noted that a lower exposure in the standard test method does not with necessity mean lower threshold for regulatory compliance as the test criteria also differ between different countries.

    One of the tests were characteristic of open plan office buildings and it was shown that the fire exposure is both shorter and lower compared to typical residential compartment tests. All standard tests that were used for comparison here exhibited both longer and higher exposure than the office building compartment test.

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    Report Exposure to facades
  • 61.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Byström, Alexandra
    Lange, David
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Wickström, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Thermal exposure to a steel column from localized fires2012Report (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 62.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Försth, Michael
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Otxoterena Af Drake, Paul
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Svensson, Robert
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Ignition of natural fuels from strikes between steel and rocks2022Report (Other academic)
    Abstract [en]

    The ignition of natural fuels by sparks from strikes between metals and hard rock is far from understood and the ignition potential of sparks from rock strikes during heavy machinery operations is disputed in the scientific literature. This study utilises a spectrally resolved technique to study the temperature evolution of metal sparks from rock strikes. The study shows that initial temperature after collision can easily reach 1500 °C and this temperature can increase additionally by several hundred degrees as rapid oxidation processes are initiated, often leading to further disintegration of the fragment. The average temperature of fragments from such collisions is here measured to 1400 – 2000 °C and the combination of temperature, size and exothermic processes makes them viable for forest litter igniting. However, ignition on forest lands is always an unlikely, although possible outcome of heavy machinery operations and should be considered in risk assessment of the activity.

    Download full text (pdf)
    fulltext
  • 63.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    A phenology-driven fire danger index for northern grasslands2023In: International journal of wildland fire, ISSN 1049-8001, E-ISSN 1448-5516Article in journal (Refereed)
    Abstract [en]

    Background: Directly after snowmelt, northern grasslands typically have highly flammable fuel-beds consisting of 100% grass litter. With green-up, the addition of high-moisture foliage leads to progressively decreasing fire hazard.

    Aims: Our aim was to create a fire-danger index for northern grasslands that incorporated grass phenology.

    Methods: We made use of 25 years of Swedish wildfire data and 56 experimental fires conducted during one full fire-season, merged with established models for moisture content and flame spread rates. Refined data on equilibrium moisture content of grass litter were obtained through laboratory tests.

    Key results: The RING (Rate of spread In Northern Grasslands) model uses cumulative air temperature as a proxy for growing season progression. Three independent functions account for impact of wind, moisture content and the damping effect of live grass, respectively. The latter results in exponentially decaying rate of spread (ROS) with the progressing season. Following the field experiments, green grass proportion as low as 10–20% (live/dead dry-mass) resulted in model-ROS so reduced that the grassland fire season could effectively be considered over.

    Conclusions: The model, calculated from standard meteorological data only, matches the experimental results and separately performed validation tests, as well as wildfire dispatch data.

    Implications: RING has been used in Sweden since 2021 and is likely applicable to other northern regions as well.

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    fulltext
  • 64.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Human activity and demographics drive the fire regime in a highly developed European boreal region2023In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 136, p. 103743-103743, article id 103743Article in journal (Refereed)
    Abstract [en]

    Organization of successful wildfire prevention and suppression require detailed information on ignition causes, size distributions and relations to weather. From a large and highly detailed dataset of Swedish wildfire incidents (n = 124 000) we assess temporal, geographical and human-related patterns over a 25-year-period (1996–2020). We find strong positive correlations between population density and wildfire occurrence, primarily caused by a wide spectrum of human activities. However, fires >10 ha mostly occurred in sparsely populated regions and were more often ignited by lightning or heavy machinery. Further, large fires had a history of long response times and insufficient mop-up, in turn intimately linked to low population density. We detect no trend over the 25-year-period in either fire weather, number of ignitions or burned area, but a dramatic decline in wildfire caused by children's play as well as by springtime burning of dead grass, a traditional fire use in rural areas. Our results indicate that irrespective of climate change, societal changes such as rural depopulation and cultural shifts are imminently important for the future fire regime in this intensely managed part of the boreal, and may warrant more attention worldwide.

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    fulltext
  • 65.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Granström, Anders
    SLU, Sweden.
    Skogsbränder och gräsbränder i Sverige: Trender och mönster under senare decennier2020Report (Other academic)
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    fulltext
  • 66.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Amon, Francine
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Vylund, Lotta
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Skogsbränder och gräsbränder i Sverige, 1996-20142016In: Brandposten, no 55, p. 22-24Article in journal (Other academic)
  • 67.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Granström, Anders
    SLU, Sweden.
    Jansson, Anna
    SMHI, Sweden.
    Böhlin, Johan
    SMHI, Sweden.
    En ny modell för gräsbrandsfara i Sverige2021Report (Other academic)
    Abstract [en]

    In northern regions, the propensity for ignition and rapid spread differ noticeably between socalled grassfires and forest fires. During early spring, fires can spread rapidly in the grass litteron open fields after just a few hours of dry weather. Potential rate of spread, however, decreaseswith the growth of new grass to virtually zero by the onset of summer. Forest fires do not exhibitthe same fuel-related seasonal dependence and fuel beds in forests typically dry more slowly.Due to these differences, there is a need for different risk assessment models for these twocharacteristic types of wildfires.This report presents a new model for grassfire danger. The model uses potential rate of spreadof uncut, un-grazed, natural grass as a proxy for fire danger. The algorithm uses current and pastweather (snow cover, relative humidity, wind speed, temperature, and irradiance) in additionto a sub-model for the progressive growth of new grass. We modify a Canadian model forcalculating moisture content in grass litter (Wotton, 2008) and Australian models (Cheney et al,1993; 1998) to account for the effect of wind and fuel moisture content on rate of spread. Thelimiting effect of grass regrowth for Swedish conditions is incorporated using 25 years dispatchand weather data combined with a set of experimental fires conducted from the time ofsnowmelt to the end of the grassfire season (Granström et al, 2000). The model is suited forhourly updates, in line with the new wildfire risk assessment in Sweden, and will beimplemented in the spring of 2021. 

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    Rapport
  • 68.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Jansson, Robert
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Measuring thermal material properties for structural fire engineering2012In: Proceedings from 15th Int Conf on Experimental Mechanics, Porto, 2012, 2012Conference paper (Refereed)
  • 69.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Lange, David
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    An investigation of the lumped capacitance assumption for unprotected steel members2014In: Proceedings of the 8th International Conference on Structures in Fire, 2014, , p. 961-968Conference paper (Other academic)
  • 70.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Lange, David
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Förstudie: Effekten av Eurokods antagande om homogen uppvärmning av oskyddade stålkonstruktioner (English2014Report (Refereed)
  • 71.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Lange, David
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Debuyser, Michaël
    Ghent University, Belgium.
    Honfi, Daniel
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Sock, Delphine
    Buildsoft, Belgium.
    Belis, Jan
    Ghent University, Belgium.
    Application of concepts of fire resistance of load bearing structural glass2016In: Structures in Fire: Proceedings of the Ninth International Conference, 2016, p. 869-876Conference paper (Other academic)
    Abstract [en]

    The use of glass as a load bearing element in structures is a growing phenomenon. Glass elements cover both beams and shear walls and its use is driven mostly by aesthetical and architectural reasons but brings other benefits considering environmental and financial aspects. Glass is a strong material but with a brittle nature which means a sudden fracture on failure with negative consequences for safety. However, with new techniques of increasing ductile behaviour and with the use of glass elements embedded in a holistic fire safety design strategy there are now several examples of load bearing glass elements in modern construction. This paper highlights some aspects of the use of load bearing glass with recent updates on the general knowledge base and the standardisation work.

  • 72.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Lange, David
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Jansson, Robert
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Albrektsson, Joakim
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    SP undersöker sambandet mellan deformation under brand och skador i efterspända betongplattor2012In: Brandposten, no 46, p. 16-17Article in journal (Other (popular science, discussion, etc.))
  • 73.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Persson, Henry
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Brandteknik, skydd (BRs ).
    Hög strålning från stora etanolbränder2013In: Brandposten, no 48, p. 24-25Article in journal (Other (popular science, discussion, etc.))
  • 74.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sokoti, Hasan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Brandon, Daniel
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Pyrolysis and thermal properties of wood and high-density polyethylene2024Report (Other academic)
    Abstract [en]

    Sample tests were conducted to obtain thermal and kinematic parameters for wood and high-density polyethylene (HDPE) that were used in a series of intermediate scale tunnel fire tests with and without water-based fire suppressions systems. The thermal properties were measured using Transient Plane Source (TPS) and Transient Line Source (TLS). The pyrolysis kinetics parameters were tested based on Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Different methods were used to obtain pyrolysis kinetics parameters. Different oxygen concentrations exposed to samples were tested and the results showed its significant influence in the charring process.

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    fulltext
  • 75.
    Sjöström, Johan
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Vermina Lundström, Frida
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Skogsbränder orsakade av skogsmaskiner2018Report (Other academic)
    Abstract [en]

    Several large wildfires in Sweden are caused by forestry machinery in operation, but there is no overview or characterization of machine-caused fires. Combining dispatch data, weather, fire danger and interviews with forestry entrepreneurs we gain a deeper understanding of spatial/temporal/weather distributions of these fires as well as their characteristics and underlying mechanisms. The average annual number of machine-caused ignitions in Sweden is estimated to 330-480 (2.0±0.4 ignitions per 1000 ha clear-felled land) of which 34.5 lead to fire-fighter dispatch. These constitute 2.2% of all forest fires and 40% of area burnt. Soil scarification causes most ignitions and the main mechanism is likely high-inertia contact between discs and large stones, causing sparks igniting dry humus/moss. This counters reports suggesting that such metal fragments cannot fulfil ignition requirements. We found a strong spatial relationship between forestry machinery ignitions and the abundance of large stones, represented by a boulder-index generated from 13500 nation-wide site inventories. Further, 75% of the dispatches occurred on days with relative humidity <45%, Duff Moisture Code >26 and Fire Weather Index >12. 75% of the total area burned when Fire Weather Index >20. Cancelling operations in stony terrain during high-risk weather situations can largely avoid the problem.

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    fulltext
  • 76.
    Sjöström, Johan
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Vermina Lundström, Frida
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Wildfire ignition from forestry machines in boreal Sweden2019In: International journal of wildland fire, ISSN 1049-8001, E-ISSN 1448-5516, Vol. 28, no 9, p. 666-677Article in journal (Refereed)
    Abstract [en]

    Several large Swedish wildfires during recent decades were caused by forestry machinery in operation, fires for which there is still no characterisation. We combined 18 years of data on dispatches, weather and fire danger and interviewed forestry workers to understand the spatial, temporal and weather distributions of these fires, and their underlying mechanisms. We estimate the average annual number of ignitions from forestry machinery in Sweden at 330-480 (2.0 ± 0.4 ignitions per 1000 ha clear-felling) of which 34.5 led to firefighter dispatches, constituting 2.2% of all forest fire dispatches and 40% of area burnt. Soil scarification causes the most ignitions and the main mechanism is likely high-inertia contact between discs and large stones, causing sparks igniting dry humus or moss, countering reports suggesting that such metal fragments cannot fulfil ignition requirements. We found a spatial relationship between forestry machine ignitions and abundance of large stones, represented by a Boulder Index generated from a nationwide dataset. Further, 75% of the dispatches occurred on days with relative humidity <45%, Duff Moisture Code (Canadian system) >26 and Fire Weather Index >12. 75% of the area burned when Fire Weather Index was >20. Results suggest machine-caused forest fires can be largely avoided by cancelling operations in stony terrain during high-risk weather.

  • 77.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Vermina Plathner, Frida
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Granström, Anders
    SLU, Sweden.
    Hur stora är växthusgasutsläppen vid naturvårdsbränning?2024Report (Other academic)
    Abstract [en]

    How large are the global warming emissions from prescribed fires in the European boreal? This report addresses emissions of greenhouse gases during prescribed fires, which are done in Sweden for increased biodiversity. Focus is on CO2-emissions during the combustion. There are large instantaneous emissions to the atmosphere. However, the CO2-debt, i.e. the difference in atmospheric CO2 if the burning is conducted or not, decreases rapidly in the years following the burn as carbon is stored in soil and growing plants. The emissions from prescribed burning on protected land can be assessed using field observations of fuel loads, fuel consumption during the fire and post fire plant/litter accretion. The net change in atmospheric CO2 is thereafter calculated from these data sets for different time since fire. Instantaneous emissions are estimated, for a characteristic fuel type, at 14.4 tonnes CO2 per hectare. After only ten years 78 % of this is again fixed in the vegetation on the forest floor, and litter. The same number 20 years post fire is 90 % and at 50 years, 98 %.

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  • 78.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Wickström, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Different types of plate thermometers for measuring incident radiant heat flux and adiabatic surface temperature2013Conference paper (Refereed)
  • 79.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Wickström, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    SP investigates thermal exposure to a steel column from localized fires2013In: Brandposten, no 48, p. 26-27Article in journal (Other (popular science, discussion, etc.))
  • 80.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Wickström, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Superposition med icke-linjära randvillkor för temperaturberäkningar2014In: Brandposten, no 50, p. 28-Article in journal (Other (popular science, discussion, etc.))
  • 81.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Wickström, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut. Luleå Technical University, Sweden.
    Superposition with Non-linear Boundary Conditions in Fire Sciences2015In: Fire technology, ISSN 0015-2684, E-ISSN 1572-8099, Vol. 51, no 3, p. 513-521Article in journal (Refereed)
    Abstract [en]

    Linear response theory is widely used in science and engineering but its use in fire sciences is rare. This communication reviews shortly the Duhamel superposition technique for solving problems in fire sciences where the response of a material maybe assumed linear but the boundary conditions (BC) are non-linear. The method can be used as an alternative to e.g. finite element methods for problems where analytical solutions are not available. Examples include temperature distribution in solids with time-varying and non-linear heat flux boundaries using a simple spreadsheet solution technique. Supplementary material contains an Excel spreadsheet solving problems with non-linear BC.

  • 82.
    Sjöström, Johan
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Wickström, Ulf
    Lund University, Sweden.
    Byström, Alexandra
    Lund University, Sweden.
    Validation data for room fire models:Experimental background2016Report (Other academic)
    Abstract [en]

    A series of room fire tests for enclosures with different wall materials have been conducted for the purpose of supplying validation data for enclosure fire models. The wall materials are varied between light weight concrete, mineral wool insulation, bare 3 mm steel, and finally insulated steel. All tests used a propane gas burner with a well-defined mass flux as a fire source. Temperatures of thermocouples and plate thermometers were measured as well as oxygen concentrations in the opening. For some tests the heat release rate (by oxygen consumption calorimetry) as well as O2, CO2 and CO concentrations were measured in addition.This report describes the instrumentation, fire scenarios, enclosure materials, and results from all the tests. All results are readily available as spreadsheet data for downloading. The report also contains short description showing the influence of different factors such as wall materials, heat release rates and burner placements.Key words: Room fires; validation; experiments; thermal properties; walls

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  • 83.
    Storesund, Karolina
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Fire Research Norway.
    Reitan, Nina Kristine
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Fire Research Norway.
    Sjöström, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Rød, B.
    UiT The Arctic University of Norway, Norway.
    Guay, F.
    INOV INESC Inovação, Portugal.
    Almeida, R.
    Danish Institute of Fire and Security Technology, Denmark.
    Theocharidou, M.
    European Commission, Italy.
    Novel methodologies for analysing critical infrastructure resilience2018In: Safety and Reliability - Safe Societies in a Changing World - Proceedings of the 28th International European Safety and Reliability Conference, ESREL 2018, 2018, p. 1221-1230Conference paper (Refereed)
    Abstract [en]

    In the field of Critical Infrastructures (CI), both policy and research focus has shifted from protection to resilience. The IMPROVER project has developed a CI resilience management framework (ICI-REF), applicable to all types of CI and resilience domains (technological, organisational and societal) allowing operators to understand and improve their resilience. IMPROVER has also developed methodologies to be used within the framework, accompanied with resilience indicators for operators to assess their technological and organisational resilience. The framework allows CI operators to incorporate resilience management as part of their risk management processes. The ICI-REF, the resilience analysis methodologies and indicators have been optimised, applied and demonstrated in a pilot implementation, focusing on the potable water supply in Barreiro, Portugal. Conclusions from the operators so far are that the indicators, well-defined and unambiguously described, are crucial for monitoring resilience activities, to ensure objective, consistent, repeatable and representative results from the assessed processes.

  • 84.
    Temple, Alastair
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sokoti, Hasan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sundberg, Peter
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Kahl, Fredrik
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Anderson, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety. RISE.
    Vermina Plathmer, Frida
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sjöström, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Development of Experimental Method for Assessing Risk of Lithium Fires Related with Fusion Reactor Lithium Cooling Loops2021Report (Other academic)
    Abstract [en]

    The aim of this project is to provide the basis for risk assessments relating to the risk of lithium leaks in the DONES project. This report firstly summarizes the current knowledge of risks and reaction features at different scales with liquid lithium. Note that the review is limited to fire behaviour of lithium in its liquid state and does not consider additional risks connected with breeding tritium or corrosive effects of impurities. Some of the questions important for this project are to limit the lithium reaction with water, limit the spread of fire started by a reaction with lithium and extinguish flame of lithium induced fires. The second part of the report consists discussion of some initial small-scale experiments, undertaken to provide a basis for limiting the extent for further larger tests, and a proposal for an experimental device where lithium reactions can be studied in a controlled environment, i.e. with controlled amount of oxygen, nitrogen or humidity in the experiment. This will then be the basis for risk assessment for liquid lithium loop in the DONES facility.

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  • 85.
    Vermina Lundström, Frida
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Sjöström, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Lärdomar från inträffade vegetations-bränder under vinterhalvåret2017Report (Other academic)
    Abstract [en]

    Although wildland fires are not common during the cold season in the Nordic countries, there is a risk for uncontrolled spread. This was proved during a mild winter in Norway in 2014, when three large fires occurred. Therefore, a fire weather forecast running during winter time could provide the rescue service with knowledge on the risk of spreading fires. In this report, data from previous fires is gathered to gain knowledge on how to modify a risk index for fire weather during the Swedish winter.

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  • 86.
    Vermina Lundström, Frida
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sjöström, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Garden structure is critical for building survival in northern forest fires – An analysis using large Swedish wildfires2023In: Safety Science, ISSN 0925-7535, E-ISSN 1879-1042, Vol. 157, article id 105928Article in journal (Refereed)
    Abstract [en]

    Despite increasing concern over wildfires in Fennoscandia, there are essentially no studies on the survivability of buildings within the wildland-urban interface of this region. We make use of four recent large-scale fires in Sweden to elucidate which factors are important for survival, using multiple logistic regression analysis of data collected at the sites. We obtained data on 187 buildings within the fire perimeters, nearly all with wood paneling and tile- or sheet metal roofing. 35 % of the buildings were lost or badly damaged. Results indicate that most buildings were approached by relatively low-intensity fire and that ignition primarily occurred through direct flame contact. The most important factor for survivability was the presence of a maintained lawn. The second most important was that no flammable material was present close to the building façade. Further, fire intensity often decreased close to buildings due to a larger portion of deciduous trees around gardens than in the surrounding forest. These factors were more important than specific features of the building itself, reflecting that the majority of buildings have combustible wooden façades. Our results suggest that the greatest potential for increasing building safety in the Swedish WUI is to keep the area immediately surrounding the building (∼5 m) free from tree litter and other flammable material. Also, since fire intensities are generally low, buildings can in most cases be defended with simple tools without compromising personal safety.

  • 87.
    Wickström, Ulf
    et al.
    Luleå University of Technology, Sweden.
    Anderson, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Sjöström, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Measuring incident heat flux and adiabatic surface temperature with plate thermometers in ambient and high temperatures2019In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 43, no 1, p. 51-56, article id 2667Article in journal (Refereed)
    Abstract [en]

    A new more insulated and faster responding plate thermometer (PT) is introduced,which has been developed for measurements particularly in air at ambient temperature.It is a cheaper and more practical alternative to water‐cooled heat flux meters(HFMs). The theory and use of PTs measuring incident radiation heat flux and adiabaticsurface temperature are presented. Comparisons of measurements with PTsand HFMs are made. Finally, it is concluded that incident radiation in ambient aircan be measured with HFMs as well as with the new insulated type of PT. In hot gasesand flames, however, only PTs can be recommended. At elevated gas temperatures,convection makes measurements with HFMs difficult to interpret and use for calculations.However, they can be used in standard or well‐defined configurations forcomparisons.

  • 88.
    Wickström, Ulf
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Sjöström, Johan
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research, Brandmotstånd.
    Byström, Alexandra
    New method for calculating time to reach ignition temperature2013Conference paper (Refereed)
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