What is the function of a SCBA operated in pressure-demand mode?

The function of a self-contained breathing apparatus (SCBA) operated in pressure-demand mode is primarily to provide a supply of breathable oxygen in an environment that may contain toxic gases or insufficient oxygen levels. In pressure-demand mode, the SCBA ensures that air flows to the wearer only when inhaling, which helps maintain a positive pressure within the mask. This positive pressure protects the wearer from the inhalation of hazardous contaminants present in the atmosphere.

In situations where the air quality is compromised or where there are harmful substances that can be inhaled, such as toxic chemicals, combustion products, or low-oxygen environments, relying on an SCBA in pressure-demand mode is crucial for respiratory protection. The SCBA system includes an air tank that holds clean, breathable air, ensuring that the wearer can safely perform tasks and navigate through hazardous environments.

While other options pertain to different functions or scenarios, they do not align with the primary role of pressure-demand SCBA systems. Enhancing visibility, filtering particulate matter, or operating at ambient pressure are characteristics associated with other types of equipment or modes of operation that are not specific to SCBAs in pressure-demand mode.