###### Abstract
The disadvantages of the current cleaning processes are directly related to efficiency, and with unsatisfactory removal: the economic cost related to the working hours of the cleaning operators, the safety of the treatment due to the high toxicity of the solvents, and environmental pollution, involving a high risk to the marine ecosystem, the emission of greenhouse gases and a high consumption of water resources. On the other hand, it can also be stated that they are cleaning methods that damage the underlying materials, affecting the vehicle's finish and supports, and forcing the extension of a train's stoppage times, which disrupts timetables and passenger transport. Research in other industrial and heritage sectors has focused on exploring new cleaning systems that minimise working times and toxicity and improve efficiency [41]. These include cryogenic CO2 'dry-ice blasting' by projection of solid CO2 in pellet form [42], or'snow blasting' liquid CO2 in mist form [43]. This technique was initially developed as a degreasing method and has evolved significantly since its introduction onto the market in the 1980s. It provides an innovative approach to surface cleaning, its effectiveness being based on three mechanisms: thermal shock through cooling, kinetic energy generated by compressed air and impact, and sublimation of the projectile [44]. The advantages of this system over other cleaning methods have been studied. Firstly, it provides an eco-sustainable approach by projecting recycled CO2, which reduces water consumption and eliminates the need for solvents that damage the environment and health [45]. In addition, it ensures the safety of the surfaces by avoiding abrasion due to the low hardness of the pellets used (2 Mohs) [46] and favours the reduction in air pressure required compared to other mechanical methods [47]. It is a versatile cleaning method, due to its ability to adapt to different parameters and delicate surfaces [48] and unique treatment, as it does not leave residues on the treated surface that would require a second washing or drying of the surface [49]. On the other hand, a comparative study with other types of spraying methods such as sand blasting or water blasting, carried out by researchers from the Department of Civil, Architectural, and Environmental Engineering of the University of Miami, found that it required 19% less energy than other techniques, in addition to reducing the average time of use by 77%, validating it as an efficient and safe technique for its application to architectural structures [50]. However, due to the nature of the projectile, CO2 cleaning recorded the highest values of greenhouse gas emissions. Although dry-ice blasting favours the reuse of surpluses and by-products, the production of this material being an inherent process in the manufacture of other gases such as oxygen, argon and hydrogen [51], reducing the release of carbon dioxide into the atmosphere is a new challenge in cryogenic studies. In the search for solutions, a collaboration between research departments arose for the adaptation of equipment designed to carry out refrigeration cycles at temperatures below \(-150\)\({}^{\circ}\)C [52; 53; 54]. This is an installation whose innovation lies in the use of ambient air as the refrigerant fluid, avoiding the environmental and economic impact of the use of cooling liquids, since air (known as a refrigerant with the code R-729) has null ODP and GWP, is plentiful and has no cost, and is harmless, non-flammable, non-reactive, and,of course, breathable, avoiding any impact on the health of the workers that employ this technology. The technology has been adapted and transferred to the medical (vaccine preservation), automotive (ultra-fast battery charging) and agri-food (food preservation) industries. Figure 1 illustrates the experimental installation designed to produce low-temperature air jets. The configuration used in the installation corresponds to a reverse Brayton cycle, comprising three consecutive stages of air compression.