Materials that contain blood or other potentially infectious materials. These materials include many of those found in biological evidence, including semen, vaginal secretions, or any bodily fluid that is visibly contaminated with blood, and all bodily fluids in situations in which it is difficult or impossible to differentiate between bodily fluids as well as any unfixed tissue or organ from a human (living or dead) that can be collected at a crime scene and stored (OSHA 2012).