In a building, when air pressure inside is higher than outside, air moves which direction?

In a building, when air pressure inside is higher than outside, air moves which direction?

• A. Air pushes in (Infiltration)
• B. Air pushes out (Exfiltration)
• C. Air remains stationary
• D. Air circulates around outside

Answer: (B)

Air moves from higher pressure to lower pressure. When the air inside a building is at greater pressure than the air outside, it pushes outward through cracks, joints, and openings. That outward flow is called exfiltration. It happens whenever indoor pressure is elevated compared to outdoors, whether due to exhaust fans, warm indoor air rising and escaping, or wind pressing on the building. If the inside pressure were lower than the outside, air would tend to flow in, which is infiltration. The other options don’t describe pressure-driven movement through the building’s openings.

Air moves from higher pressure to lower pressure. When the air inside a building is at greater pressure than the air outside, it pushes outward through cracks, joints, and openings. That outward flow is called exfiltration. It happens whenever indoor pressure is elevated compared to outdoors, whether due to exhaust fans, warm indoor air rising and escaping, or wind pressing on the building. If the inside pressure were lower than the outside, air would tend to flow in, which is infiltration. The other options don’t describe pressure-driven movement through the building’s openings.