Final answer:
The essential personal protective equipment (PPE) for environments with toxic particles is a HEPA-filtered respirator, accompanied by engineering controls like biological safety cabinets with HEPA filters.
Step-by-step explanation:
The most important PPE to wear when working in an environment where toxic particles may exist is a HEPA-filtered respirator. This type of respirator has high-efficiency particulate air (HEPA) filters that can effectively trap toxic particles and prevent them from being inhaled. In addition to wearing a respirator, it is essential to implement engineering controls, which might include the use of biological safety cabinets that also utilize HEPA filters to protect the working environment. Examples of environments requiring stringent controls and protective equipment include BSL-4 laboratories and areas dealing with radioactive materials or infectious agents such as the Ebola virus. Personal protective equipment (PPE) might also extend to full-body protective suits with their own air supply, as illustrated in the referenced figures showing personnel in protective clothing while handling hazardous substances.