The "D Class" refers to a category of personnel used by the SCP Foundation, a fictional organization in a collaborative writing project. These individuals are often recruited from prisons or other institutions and are typically used for testing and experimentation involving SCP objects, which are anomalous items or entities. D Class personnel are usually expendable, meaning their safety is not a priority during these experiments. The primary purpose of D Class is to provide the Foundation with data on the effects of various SCPs. Due to the dangerous nature of these experiments, D Class personnel often face significant risks, including injury or death. This system raises ethical questions about the treatment of individuals in such roles.