Which is one of the four basic components of self-contained breathing apparatus (SCBA)?

The correct answer is the regulator, which is a crucial component of a self-contained breathing apparatus (SCBA). The primary function of the regulator is to reduce the high-pressure air from the cylinder to a breathing pressure that is safe and breathable for the user. This ensures that firefighters can receive adequate airflow while performing their duties in hazardous environments, such as during a fire or rescue operation where toxic gases may be present.

In addition to the regulator, an SCBA also includes a cylinder that stores the compressed air, a facepiece that allows the user to inhale the filtered air, and a harness that secures the SCBA to the firefighter. Each of these components plays a vital role in the overall functionality and safety of the SCBA, enabling effective protection and respiratory support in critical situations.