## 1 Introduction
Responders were divided into groups, with one group using no protective mask, the second group using a protective mask with the filter placed in the front, and the last group having the filter placed on the side of the protective mask. The results showed that for this purpose, the use of a protective mask with a filter placed in the front is preferable. A filter placed in the lateral part reduces the mobility of one of the rescuer's hands. However, the study focused only on the selected characteristic of the protective mask as well as the specific activity [8]. The team of authors addressed the potential use of full-face gas protection masks used in the military in the context of the SARS-CoV-2 pandemic. Testing focused on evaluating the Airboss Low Burden Gas Protective Mask in comparison to disposable protective drapes. The aim of the study was to determine whether the protective mask used in the military environment is suitable for use in the civilian sector. The testing was based on ten evaluation criteria. These criteria were, for example, ease of donning, initial comfort, fogging, sealing, or subjective confidence in its protection. A relatively large sample of 61 respondents participated in the testing. The test results confirmed the suitability of the use of full-face gas protection masks used by the military in hospital and civilian environments. The use of this type of protective mask also reduces the cost of procuring disposable protective drapes and overall logistics. Gas protective masks can be easily disinfected and reused [9]. [PERSON] and [PERSON] [10] conducted a subjective evaluation of three Czech and nine foreign protective masks. The subjective criteria included the size of the field of vision, distortion of the view through the mask, vision under the feet, tolerability of the inner half mask, qualitative characteristics of the clamping system, manipulability of the clamping system, the effect of the filter on the user's vision through the mask, the subjective tightness of the mask, whether the mask fits well on the face, intelligibility when speaking, and respiratory resistance. A disadvantage of this evaluation was that the individual subjects who tested the gas masks did not in all cases have a satisfactory protective mask size [10]. However, the above studies provide sufficient evidence to confirm the importance of subjective testing and assessment. The inclusion of subjective evaluation of personal protective equipment and products in general is one of the prerequisites for a comprehensive quality assessment. Quality management, according to the STN EN ISO 9000:2016 [11] series of standards, is a prerequisite for product conformity assessment [12; 13]. Quality control, according to ISO standards, is also required by Regulation (EU) 2016/425 of the European Parliament and of the Council of 9 March 2016 on personal protective equipment and repealing Council Directive 89/686/EEC [14]. Protective masks fall under personal protective equipment and are used to protect the face, eyes, and respiratory organs. According to that Regulation, such equipment should be designed in such a way that any restriction of the field of vision, face, or respiratory organs is reduced to a minimum. At the same time, these devices should be designed to prevent chafing and ensure that the clamping systems do not cause problems for users for the needs of rapid deployment and use [14]. The aforementioned properties can also be tested using subjective criteria. From the above review of studies focusing on the testing of gas protection masks, it is possible to infer some gaps in research focusing on subjective parameters and evaluation. Relatively little attention has been paid to the testing of subjective characteristics. The objective side of the evaluation of protective equipment plays a more significant role [1], but to ensure a comprehensive evaluation, it is essential to consider the subjective side as well [12; 13]. The analyzed studies dealing with subjective evaluation had several shortcomings.