Which measure helps prevent the spread of contaminants between spaces by controlling air movement?

• A. Pressure balancing between spaces
• B. Filtration alone
• C. Increasing outdoor air without filtration
• D. Reducing ventilation to save energy

Answer: (A)

Controlling how air moves between spaces is achieved by establishing pressure differences. Air naturally flows from higher pressure to lower pressure, so by setting the pressure in adjacent spaces appropriately you can direct airflow to hinder contaminants from spreading from one space to another. This is why balancing pressure between spaces is the most effective measure for preventing cross-contamination: it dictates the path air takes, independent of filtration or ventilation rate.

Filtration helps remove contaminants from air, but it doesn’t stop air movement and can be bypassed by leaks if the pressure relationship isn’t controlled. Increasing outdoor air without filtration could introduce contaminants, and reducing ventilation can worsen spread by letting contaminants accumulate.