Citation: Kaczorek-Chrobak, K.; Fangrat, J. Electric Cable Construction Parameter and Its Potential to Foresee the Cable Fire Properties. Materials 2023, 16, 1689. https://doi.org/10.3390/ ma16041689 Academic Editor: Jun Yan Received: 5 October 2022 Revised: 7 February 2023 Accepted: 14 February 2023 Published: 17 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Electric Cable Construction Parameter and Its Potential to Foresee the Cable Fire Properties Katarzyna Kaczorek-Chrobak * and Jadwiga Fangrat * Fire Research Department, Instytut Techniki Budowlanej, Filtrowa 1, 00-611 Warszawa, Poland * Correspondence: k.kaczorek-chrobak@itb.pl; Tel.: +48-22-56-64-460 Abstract: A cable parameter related to the volume of effective non-combustible content, Ω, is proposed, which depends on the ratio of non-metallic, non-combustible component volume to non- metallic, combustible component volume, and the effective area of heat transfer within the cable during the combustion process. The correctness of the proposed cable parameter for circular cables is confirmed by tests and the determination of Spearman’s correlation. High Spearman’s correlation factors (close to −1) were obtained for total heat release and total smoke production as a function of the Ω cable parameter. The Ω cable parameter might be used in selecting cable samples for large geometric-scale fire testing within the same cable family. Keywords: cable parameter; cable fire properties; reaction to fire of cables; fire safety 1. Introduction Electric cables are important parts of buildings and any transportation system, such as vehicles, aircraft, and ships. The huge volume of electric cables installed in such objects, and the types of materials used for their production, have a level of environmental impact. They strongly influence fire safety as well. Such fires may present negative safety and environmental impacts, and may exert a strong influence on the external environment and surroundings. Energy conservation and safety needs are contradictory in some situations, and therefore a proper balance between them is necessary [1–3]. The fire properties of electrical cables have gained growing interest since they were included in the group of building products in the EU in 2011. There are kilometers of electrical cables installed in each building; therefore, they constitute a significant factor in its fire safety. The large number of cables installed not only strongly increases their fire load but may also facilitate flame spread over a long distance (both horizontal and vertical) in the case of fire [4–6] and increase the potential fire toxicity [7]. Cables are an indispensable part of present life, but often pose a potential fire hazard. They provide electricity and signals to various receivers and, based on their end-use application, may be clearly divided into types according to their purpose. Cables are complex objects because they consist of insulation and sheaths made of polymeric materials of various chemical structures, thicknesses, and additives [8]. The use of electric cables has brought to the forefront the need to protect against electric shock, overload and short-circuit current, switching overvoltage, lightning, and numerous heat effects [9], including fire. The fire properties of electric wires and cables have been extensively studied, both experimentally and theoretically. A valuable review has been presented [10] with the fol- lowing summary: ‘the complex role of the conductor, specifically whether it is a heat source or heat sink, in the ignition, flame spread, burning, and extinction, has been emphasized throughout this review.’ And ‘a deeper understanding of fire phenomena in real wire and cable is still quite challenging, and attempted inferences for real wire fires based on the qualitative or semi-empirical analysis of limited laboratory data are not yet convincing Materials 2023, 16, 1689. https://doi.org/10.3390/ma16041689 https://www.mdpi.com/journal/materials