What is meant by glowing combustion?

Glowing combustion refers to a type of combustion that occurs in the absence of a flame, which is accurately represented by the chosen answer. In this process, solid materials, such as charcoal or certain metals, can continue to burn at high temperatures without producing an open flame. This situation often results in the material glowing red or orange due to the heat generated from the chemical reaction occurring on its surface.

While the other options discuss various combustion processes, they either describe phenomena that involve flames, relate exclusively to certain fuel types, or focus on the release of toxic gases. For instance, visible flames are characteristic of flames generated through different combustion processes, but they do not occur in glowing combustion. Similarly, limiting combustion to only liquid fuels does not apply, as glowing combustion can take place with solid materials, as mentioned. Lastly, while some combustion reactions may release toxic gases, this aspect does not define glowing combustion specifically. Understanding glowing combustion helps clarify its distinct characteristics in fire dynamics and investigation contexts.