Which of the following types of respirators requires special training to use?

Type C respirators are considered air-supplying respirators and require specialized training for their proper use. These respirators are typically utilized in environments where there is a significant concentration of hazardous substances, including asbestos, and they rely on a supply of air from an external source. This necessitates training on how to use, maintain, and monitor the respirator effectively, as well as understanding the safety and regulations associated with their use.

In contrast, standard surgical masks and dust masks are generally designed for lower risk scenarios and do not require the same level of training or understanding of complex operating procedures. These simpler masks are meant primarily for general particle filtration and do not provide the same level of protection or air supply management as Type C respirators. Therefore, they can be used effectively without the extensive training required for more complex respiratory protection systems.