Abstract The given paper revolves around the theoretical knowledge needed for the efficient functioning of every member of a newly formed arson investigation unit. The character of their work presupposes the comprehensive investigation of different types of fires, main causes for their appearance, and substances which could be dangerous. For this reason, the given article presents a theoretical framework needed to understand the nature of fire, its main physical properties, three basic elements that make up a fire triangle, the oxidation process, and factors that might impact the fire, rate of fire spread, etc. This very paper incorporates the basic theoretical knowledge needed for a member of the arson investigation unit. The work starts with an introduction that outlines the major concerns which will be discussed; there is also the body that covers the main points and the conclusion which summarizes the key assumptions and emphasizes the unique importance of this very data. Ignition and Burning Processes The functioning of every member of an arson investigation unit helps to determine the causes for the appearance and development of fire. The improved comprehending of the nature of these processes results in the introduction of more efficient measures to struggle with fires and in the enhanced preventive measures aimed at the improvement of fire security in the area. For this reason, the deep knowledge of the nature of fire and its main peculiarities is crucial for every member of an arson investigation unit. The theoretical knowledge suggested below will help to improve understanding of these basic issues and result in the more efficient functioning of a certain investigator. Analyzing fire as a physical phenomenon, we should mention several unique properties and characteristics. Every fire investigator should understand the basic principles of combustion. Besides, this process could be described as the chemical reaction between the oxygen that could be found in the atmosphere and any sort of fuel that could be found nearby (Harris, n.d.). For this sort of reaction to start, a significant ignition temperature should be achieved. Thus, every sort of fuel has its ignition temperature and this knowledge is crucial for the improved comprehending of the nature of fire and the ability to predict its appearance. Thus, the above-mentioned physical characteristics of fire indicate that there is a need for fuel, heat, and oxygen for a reaction to happen and fire to appear. These three basic elements comprise the so-called fire triangle (Burnette, n.d.). In case these three elements are present and can interact a fire might occur. At the same time, if to remove one of the elements of the fire triangle, the chemical reaction will not start, or it will stop. For this reason, knowledge of these basic elements will help to suppress the fire. Therefore, as stated above, the presence of oxygen is one of the key factors for the appearance of fire. When the oxygen reacts with a certain fuel, we could observe the oxidation (“Chemistry of combustion,” n.d.). In the broad meaning, the process could be defined as the loss of electrons in the course of the reaction. However, if to apply the given term to the process of combustion, we could also say that the reaction between fuel and oxygen characterized by high temperatures and the formation of new substances might be called oxidation. It destroys the structure of obj