## 1 Introduction  
Water transport is an integral part of many recreational activities, both as an aid to access recreational opportunities and as a recreational activity itself. In inland and sea waters, small recreational units are used for recreational transport. These include yachts, sailboats, kayaks, pedal boats, and pontoons. Consumer interest in this type of vessel conduces the increase in their production and the continuous expansion of this fleet, which has increased from 1.3 million units in 2007 to almost 40 million in 2020. Taking into account the data published annually by the International Council of Marine Industry Associations--ICOMIA--the manufacture of these units has increased from 968,185 units in 2007 to 5,386,905 in 2017 [1]. About 22-24 thousand recreational units are produced annually in Poland. The value of exports of motor yachts in 2020 amounted to PLN 2 billion. Poland's main partners in this industry, in terms of the value of exported goods, are the USA, Germany, France and the Netherlands. According to the data of the Polish Economic Institute [2], Polish exports from January to September 2021 were 38 percent higher than in the corresponding month period of 2019. The essential safety requirements for the design and construction of recreational vessels are set out in the relevant regulations (for Poland [3]). These regulations do not clearly indicate the type and kind of material for their structures (except for the description of insulating materials in the engine room of the vessel SS 31. Section 1). It follows from the indications in this paragraph that these materials are non-combustible. Non-combustible materials are those which, when subjected to tests under specified conditions for a specified time, do not ignite and do not give off flammable gases, which could be ignited by a flame in the vicinity, and do not give off heat in such quantities as to increase the temperature to certain values [4]. This is a very important issue because fire is one of the greatest dangers that threatens vessels. Therefore, the task of designers is to construct individual elements of the vessel in such a way that they are resistant to fire. In addition, in accordance with the applicable safety regulations, the unit must be designed so that in the event of a fire, the structure retains its load-bearing capacity and the ability for rescue services to quickly reach the person in danger. The materials intended for recreational vessels should not pose a risk to people by emitting toxic smoke in the case of fire. The most important regulations related to the fire safety of vessels, i.e., the International Convention for the Safety of Life at Sea--SOLAS, the International Code for the Application of Fire Test Procedures--and the IMO FTP Code, mainly apply to marine vessels. However, fire-related accidents also involve recreational units. In the years 2014-2020, the European Maritime Safety Agency--EMSA--recorded a total of 723 accidents on vessels in European waters, including 16 related to fires Figure 1 [5]. The United States of America has the largest fleet of recreational vessels, and for this reason, they also have the largest number of reported and recorded accidents. Between 2012 and 2021, there were 43,570 accidents in U.S. waters, of which 2635 involved fires (Figure 2). Figure 1: Accidents on yachts in 2014–2020 according to European Maritime Safety Agency—EMSA. When analyzing statistical data on accidents in recreational vessels, it should be noted that, regardless of the water area of the analysis, fires are not among the most common hazards on board. They are relatively rare and are most often associated with:  
* A fire in the hull resulting from improper use of equipment or a leaking gas system. * A fire in the engine compartment resulting from improper or insufficient engine servicing and related fuel leaks [7,8]. * A fire in the electrical installation as a result of overloading the network and improper or insufficiently frequent checking of the electrical installation [9, 10, 11].