Air Systems Cleaning Specialist (ASCS) Practice Exam

In an exhaust system with a fan near an outside air intake, what is a potential source of cross-contamination?

1. Thermal drift

2. Stratification

3. Capture of exhaust air

4. Negative pressure in the exhaust duct

The correct answer is: Capture of exhaust air

The correct answer highlights the issue of exhaust air capture as a potential source of cross-contamination in an exhaust system where a fan is positioned near an outside air intake. This situation is problematic because if the exhaust system is not properly designed, maintained, or operated, there is a risk that exhaust air can be drawn into the intake alongside fresh outside air. This scenario is particularly concerning in environments where the exhaust air may contain contaminants, such as odors, volatile organic compounds (VOCs), or other harmful substances. The design should account for maintaining air pressure differentials that can prevent this cross-contamination from occurring. This means ensuring that the airflow dynamics do not create a scenario where exhaust air is unintentionally pulled into the intake system, which could compromise indoor air quality and safety. Proper airflow management and equipment placement are critical to preventing this negative impact. The other options are related concepts but do not specifically indicate a direct source of cross-contamination in the context of exhaust and intake systems. For example, negative pressure in the exhaust duct could contribute to issues, but capturing exhaust air is a more direct mechanism leading to cross-contamination. Stratification and thermal drift focus on temperature and pressure changes rather than air quality implications related to the mixing of exhaust and intake air