What is the minimum type of respirator required in a Class I Negative Pressure Enclosure with an asbestos fiber count of 8.5 fibers per cubic centimeter?

The correct answer is a Type "C" respirator with a backup HEPA filter. This type of respirator is specifically designed for environments with higher levels of airborne contaminants, such as asbestos fibers. The critical factor here is the asbestos fiber count of 8.5 fibers per cubic centimeter, which exceeds the limits that would be safely managed by lower-level respiratory protection.

Type "C" respirators are equipped with a positive pressure system and are designed to offer a higher level of protection compared to other types, including those that might rely solely on passive filters or mechanical devices. The inclusion of a backup HEPA filter further enhances safety by ensuring that even if the primary filtration fails, a secondary safeguard is in place to prevent inhalation of harmful fibers.

It's important to recognize that in scenarios involving asbestos exposure, providing the maximum respiratory protection possible is essential. This is due to the serious health risks associated with asbestos, which include lung cancer and mesothelioma. Therefore, a basic dust mask and options such as a full-face mask without filters would not offer adequate protection, as they do not meet the necessary filtration capabilities required for the hazardous level of fibers present.