There are three main classes of Biological Safety Cabinets (BSCs): Class I, Class II, and Class III. Each class offers different levels of protection and containment, making them suitable for different applications and risk levels. Class I BSCs provide primary protection for the user, Class II BSCs provide primary protection for the user, the environment, and the product, while Class III BSCs offer the highest level of containment and are used for handling highly hazardous agents.