Which statement describes pressure systems in relation to infiltration?

• A. They worsen infiltration
• B. They are irrelevant to infiltration
• C. They help reduce infiltration
• D. They require open discharge

Answer: (C)

Maintaining a higher indoor air pressure relative to outdoors reduces infiltration. When the inside pressure is greater, air tends to push outward through cracks and leaks in the building envelope, making it harder for outdoor air to sneak in. So the net amount of outside air entering the building through leaks decreases. If the system created negative pressure inside, infiltration would increase as outdoor air is pulled in to balance the pressure difference. The other options aren’t accurate because pressure differences do affect infiltration, and open discharge isn’t the mechanism needed to reduce it.