Candidate Physical Ability Test (CPAT) Practice Test

Self-contained breathing apparatus are primarily designed to operate in which mode?

1. Negative pressure mode

2. Positive pressure mode

3. Variable pressure mode

4. Vacuum mode

The correct answer is: Positive pressure mode

Self-contained breathing apparatus (SCBA) are primarily designed to operate in positive pressure mode. This design is crucial for ensuring the safety and effectiveness of the equipment in hazardous environments, such as those encountered by firefighters and emergency responders. In positive pressure mode, the SCBA maintains a constant airflow that is greater than the ambient atmospheric pressure. This means that any pressure difference is directed outward, preventing contaminated air from entering the mask. This is particularly important in smoke-filled or otherwise toxic environments where inhaling unfiltered air can have serious health consequences. Additionally, the positive pressure design enhances the comfort and security of the SCBA wearer, as it minimizes the chances of inhaling hazardous substances during high-stress situations. This feature allows responders to focus on their tasks without the concern of breaching the equipment's integrity. The other modes mentioned do not provide the same level of protection. Negative pressure mode would create a risk of contamination, as it relies on the wearer's ability to create a seal, which can be compromised under certain conditions. Variable pressure and vacuum modes do not align with the primary purpose and safety requirements of SCBA in emergency scenarios.