Final answer:
The third primary type of BSC is the Class III Biological Safety Cabinet, designed for highly infectious agents with gas-tight features and specialized filtration and decontamination systems to ensure safety.
Step-by-step explanation:
The third primary type of SCIF referred to in the question is typically the Class III Biological Safety Cabinet (BSC), although the student seems to have referred to SCIFs, which relates to intelligence facilities, when they likely meant BSCs. Nevertheless, focusing on BSCs, the Class III BSC is a gas-tight enclosure designed to work with highly infectious agents, such as those found in BSL-4 labs.
This type of cabinet protects laboratory personnel, the environment, and the material within the cabinet, as it utilizes a double-door system for material passage that can be decontaminated between usages. All air within the Class III BSC is passed through one or two HEPA filters and an air incineration system before being exhausted directly outdoors.