Introduction
Residential fire is a dangerous event that can lead to serious consequences. The investigation of arson from the point of ignition to its spread is essential to identify the fire’s nature, its growth, and its further propagation (Caulton 2017a). This paper examines the Christmas tree fire presented in the given video, paying special attention to the behavior of the fire. To support the arguments, the paper will also refer to scholarly literature and technical terminology.
Ignition
In the video, ignition occurs rapidly and spontaneously. As this is an open fire, the combustion process proceeds freely, exhibiting a smooth flow. The flame cannot be characterized as having explosive reactions with flares. It quickly moves in all directions, striving for openings or cracks in the building. Subsequently, through such openings, the flames can spread to nearby buildings or neighboring territory (National Fire Protection Association 2004). The speed with which the ignition process proceeds depends on the area of the building, the existing conditions for the exchange of gases with the environment, and the properties of the burning materials.
Focusing on the presented type of combustion, it is possible to note that the width of the ignition front and its perimeter are constantly increasing. They have different directions, moving at an uneven speed. This is due to the materials involved in the fire, the dimensions of the flame itself, and the conditions in which heat exchange takes place (Tinsley & Gorbett 2013). Here, the wind is not a factor; thus, its potential impact on speed and direction does not affect the fire in the given video. The boundaries of the ignition are established during the formation of the main front of the fire.
Heat and Temperature Transfer
The dry Scotch pine tree acts as a medium that contributes to and increases the fire. Since the situation occurs in a residential building, the flow and supply of air are controlled by a ventilation system. According to Fernandez-Pello et al. (2015), this means that limited oxygen content in the room with a simultaneous excess of combustible materials and substances leads to temperature transfer and heat. In this case, the spread of the fire depends on the area of the supply orifices and the airflow that comes through the mechanical ventilation system (Almirall & Furton 2016; Belcher 2013). As there is an excess of oxygen in the room, the combustion process depends entirely on the fire load. In terms of its parameters, this fire is similar to a wildfire that may be observed in an open space (Wang, Black & Zhao, 2013). Courty and Garo (2017), as well as Xin and Huang (2013), emphasize that high temperatures during a fire inflict the greatest damage. Therefore, high temperature is considered the fire’s main characteristic, along with the smoke.
Flame and Fire Spread
All four fire stages may be seen in the video: ignition, growth, development, and burnout (Reporter’s guide: all about fire 2018). The growth rate of the fire area is an important parameter in the investigation process (National Fire Protection Association 2004). Knowing this factor makes it possible to determine the speed needed to increase the consumption of extinguishing agents to stop the spread of combustion and then eliminate the fire (Caulton 2017b; Dennett 2013). In the study of fires, the linear velocity of the propagation of combustion is determined in all cases since it is used to obtain data on the average speed in the burning of typical objects (Dennett 2013). In this video, the spread of the fire from the point of origination occurs at an uneven rate in different directions.
Here, it is evident that the fire spreads to the ceiling and covers the majority of the surface. After that, it causes thick smoke and further propagation of combustion. The next fire development stage is associated with throwing over the walls that flash quite rapidly as well. According to Chi, Lu, and Ji (2017), real-time multi-feature–based fire-flame detection cameras show that the period between ignition and flashover is limited to a few seconds. The video demonstrates that the fire becomes fully developed in less than 30 seconds (Graziano 2006).
The maximum rate of fire spread is observed when the flame front moves towards the openings through which air exchange takes place. At the same time, the fire front moves along the fire load, which has a high coefficient of combustion surface (Fairgrieve 2008; Hadjisophocleous & Mehaffey 2016). The last stage of burnout implies that the temperature decreases and the fire become less intense (Crewe et al. 2014; Quintiere 2017). In the video, decay happens when the fire spread reaches the objects in the room and then the floor. The last seconds show that the fire goes out in a total of 48 seconds.
With the above observations in mind, it should be stressed that fire spread develops quickly, presenting special damage. Daeid (2005) considers that the maximum spread direction is taken as the speed of propagation of combustion in the time interval under study. Bane et al. (2013) claim that by being aware of the distance from the place of the occurrence of combustion to the boundary of the fire area, it is possible to determine the displacement of the combustion front. Since no additional impact was made on the spread of the fire, its development is characterized by a steady spread.
Conclusion
In summary, it should be emphasized that this paper analyzed the dry Scotch pine tree arson based on the given video. It was revealed that all four stages of fire development were present, including ignition, growth, full development, and decay. The ignition occurred spontaneously and flashed on the ceiling and then down to the floor. Before the fire decayed, the flame enveloped the walls and the objects in the room. In less than 50 seconds, the fire burned everything in the room and caused significant damage.
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