What classification includes fires that occur due to natural causes or human error?

The classification that encompasses fires occurring due to natural causes or human error is unintentional fires. This category is used to describe events that are not deliberately set and arise from unintentional actions, such as accidents or incidents that lead to fires, often without malicious intent. Examples include fires caused by electrical failures, improper disposal of materials, or natural events like lightning strikes.

In contrast, intentional fires are deliberately set, while undetermined fires have uncertain causes that do not clearly fit into intentional or unintentional categories. Technical failure fires typically refer to incidents stemming from equipment malfunctions but do not broadly cover the range of natural causes or broader human errors. Unintentional fires effectively capture the essence of accidental fire incidents, aligning with the classification presented in the question.