The term "illuminant" is often employed in literature to denote substances that not only produce light but can also generate considerable heat. For example, in one instance the illuminant is highlighted for its dual role in lighting and heat production, as noted in [1]. In another reference, the focus is on the technological aspect of its generation, where specialized generators are used to produce the gas that serves as the illuminant [2]. This dual emphasis on both natural radiance and engineered production illustrates the term's versatile application in describing materials essential for illumination and thermal output.