###### Abstract
[16] also noted the same problem in a prototype of smart survival clothing intended for use in the Arctic environment. The capacity of the battery used in their experiment was sufficient for 30-40 min of heating only. For this reason, researchers are constantly striving to eliminate the aforementioned limitations of electrically heated clothing by producing and conducting research on new prototypes. Works on smart clothing also concern conductive paths that are important for textile heating systems, due to the fact that they may be damaged during the production process [17]. Many researchers have been trying to improve smart clothing. For instance, [PERSON] et al. [18] conducted comparative research on the use of printed graphene, nanotubes, and silver electrodes in textiles. They developed electrically conductive paths printed on three textile substrates. Their research focused on polymethacrylic acid (PMMA) and fluorovinylidene (PVDF) as the primary polymeric materials, which were previously used to print electronic circuits on glass substrates. The results showed that samples containing 3%wt of the carbon nanotubes in PMMA on an aramid fiber substrate provided the best adhesion and resistance to bending and washing. It has been pointed out that such electrically conductive paths have the potential to be used in smart clothing applications. Another example is the use of flexible transparent electrodes (FTEs) with embedded metal meshes, which are produced by 3D printing. The printing process, using a liquid substrate driven by an electric field, makes it possible to obtain metal meshes and, consequently, flexible transparent electrodes characterized by very good optoelectronic parameters. The built-in metal structure shows excellent mechanical stability and adaptability to the environment in various difficult working conditions [19; 20]. In another example, researchers proposed a technique for fabricating high-performance transparent glass heaters (TGH) by means of microscale 3D printing with a thick layer of silver paste with an electrically driven liquid substrate (LS-EFD). The representative high-performance transparent glass heaters (TGH) described by the researchers exhibit uniform and stable heating performance, very good environmental adaptability, and excellent mechanical strength. All the advantages of TGH are related to the production of high-resolution silver gratings with a high aspect ratio on a glass substrate using a thick-layer silver paste [21; 22]. [PERSON] et al. [23] proposed a method of manufacturing nonwoven inserts with aerogel and PCM for protective clothing against cold, which are to support human thermoregulatory functions and prevent clothing from getting wet with sweat. Thanks to the use of PCM, these inserts can regulate the thermal insulation of clothing, similar to electric heating inserts. However, their operating time was quite short, as it depended on the heat capacity and mass of the PCM used. Electric heating inserts are more effective in this regard and provide a wider range of temperature regulation under clothing, but, unfortunately, they require a power source. The paper by [PERSON] et al. [23] compared the cold protection effectiveness of the inserts based on the results of thermal conductivity tests due to the fact that the produced inserts differed significantly in thickness. In the current publication, the insulating properties of electric heating inserts were evaluated based on the results of thermal resistance tests. In the presented research project, it was assumed that heating elements in clothing for mountain rescuers should be placed in a suit with a structure that allows heating inserts to make contact with the body through the underwater. The location and size of the heating inserts were subject to consultation with rescuers, and thus they were specially designed taking their requirements into account. This publication presents the results of research on heating inserts developed with the purpose of being integrated into the suit.