## 1 Introduction  
One of the major challenges in clinical practice is the need for the reduction of hospital-acquired infections (HAIs). The total amount of annually diagnosed HAI cases in the USA is 1.8 million cases, where, for almost 100,000 patients, the infection is lethal. It should be underlined that breast cancer, AIDS, and car accidents together take fewer lives annually than HAIs [1]. Therefore, the scale of this problem encourages various agencies and companies to develop solutions, providing a significant reduction of this issue. Recently performed studies showed that the issue of HAIs is one of the most important causes of extended hospitalization due to additional therapy or even deaths [2, 3, 4, 5, 6]. As it is identified in a significant fraction of patients (even more than 30%), it is addressed using various approaches. While analyzing the surveys, one can point out the most often identified pathogens, _Staphylococcus aureus_, _Escherichia coli_, _Klebsiella pneumoniae_, and _Pseudomonas aeruginosa_; however, this list changes when one focuses on certain medical procedures and the patient's age. It should be underlined that the presence of antimicrobial resistance (AMR) requires the application of new-generation drugs, yet at some point, no therapy is effective. Therefore, the means to reduce infection risk must be taken. As studies have proven, no patient contact is necessary to contaminate hospital staff with the bacteria in the room; hence, all possible pathogen transmission paths must be cut at every level. Thus, it becomes clear that an essential role of infection reduction may be the equipment if bacteria properties of the surface are implemented. Progress in hospital equipment development is enabled by the introduction of technical solutions providing new or improved functionalities. Also, better safety features are available, particularly in reducing the bacteria survival ratio. As the companies aim to meet the needs of the market, various solutions are tested in order to verify the potential usefulness of various substances to obtain a bacteriostatic film over the equipment's surface. One promising solution is nano-silver (silver nanoparticles--Ag NPs)-based antibacterial solutions [7; 8; 9; 10; 11; 12]. In particular, polymer-based coatings containing nanoparticles may be a very useful approach [13]. The acrylic-based paint containing silver nanoparticles was one of the first selections. The bacteriological tests using _Escherichia coli_ ATCC25922 (according to ISO 22196:2007 standard [14]) showed satisfying efficacy of the investigated film in terms of bacteriostatic properties, with an R value of 5.30 log (78.3%). Also, the results of the preliminary test were promising, while the obtained coverings of the equipment made of aluminum revealed satisfying adhesion and homogeneity. However, the reliability verification of the surface is one of the major issues that the producer has to evaluate. The expected lifetime of such products must be not less than 5 years. As the unique environment is considered in terms of the conditions that the material has to show resistance to, application-tailored test procedures providing insight into the degradation process of the bacteriostatic film have to be developed. In order to perform time-accelerated tests of the developed coating, a customer-tailored protocol was developed, as standard protocols appeared to be insufficient in terms of nanoparticle-based thin film coverings. In principle, the conditions typical for hospitals had to be taken into account, so adequate exposure and degradation methods were chosen. One has to be aware that the test methods of the deterioration of films made of nanomaterials must be adequate for the investigated object and phenomena. Therefore, some standard-defined test solutions are not sufficient in terms of the required outcome. The list of both the exposure method and the test techniques is given in the following chapter.