Which part of the face piece helps to maintain a positive seal during use?

The face seal is crucial for maintaining a positive seal during the use of a self-contained breathing apparatus (SCBA). This component ensures that the face piece fits snugly against the contours of the user's face, preventing any air leaks that could compromise the safety and effectiveness of the breathing apparatus. A proper seal is essential for protecting the user from inhaling harmful contaminants in the environment, especially in hazardous situations like firefighting or rescue operations.

In contrast, other components like the lens provide visibility and protection to the eyes but do not contribute directly to maintaining an airtight seal. The nose cup is important for maintaining comfort and directing exhaled air, but it does not encompass the entire face, which is necessary for a complete seal. The head harness plays a role in securing the face piece in place but does not itself create the positive seal; it merely helps to keep the face piece positioned appropriately on the user’s face. Thus, the face seal is the key component that directly affects the integrity and safety of the breathing apparatus.