The issue of danger emanating from industrial devices with combustible gases has been considered in the linear multidimensional continuous space of dangerous factors. Dangerous factors are categorized into factors associated with industrial devices and the physical-chemical properties of gases that these devices contain. The actual existing combustible gases are characterized by numerical discrete properties such as molecular mass, specific heat of combustion, etc. An abstract model space of gases is represented in the space of dangerous factors by points whose coordinates are the physical-chemical properties of gases. Given the continuity of the space of dangerous factors, actual gases will be represented by individual points within this space or regions in which certain properties, for example temperature, density, volume, are continuously changing. In addition, there would be a large number of points at which the properties of gases are incompatible, that is such that are impossible for real gases. This has allowed us to consider the issue of danger emanating from combustible gases from some general positions. Thus, using the methodology of p-functions has made it possible to split the space of dangerous factors into dangerous and safe parts. It was also possible to identify the border regions in which the task of determining the hazard from a device is incorrect. That means that some variation of dangerous factors within the accuracy known about them leads to different, mutually exclusive conclusions about danger. Such areas are termed the regions of questionable decisions. It has been found that the regions of questionable decisions may be complex in shape and their size depends on the accuracy that is inherent in the quantitative values for dangerous factors. An algorithm for constructing regions of questionable decisions has been developed that could define whether a device containing gas belongs to a region of questionable decisions. It has been shown that determining whether a device is associated with a region of questionable decisions is a numerical problem with an unambiguous solution