What happens in a sealed mine area when barometric pressure increases?

• A. Decrease in barometric pressure, seals will breathe out.
• B. Increase in barometric pressure, seals will breathe in.
• C. The area vents to atmosphere regardless of pressure.
• D. No change occurs in a sealed area.

Answer: (B)

When barometric pressure increases outside a sealed mine area, the pressure on the outside becomes higher than the pressure inside. Air moves from higher to lower pressure to balance things, so air flows into the sealed area through the sealing, and the seals are said to breathe in. This inward flow happens because the interior is relatively less pressurized than the outside after the pressure rise. The idea that the area vents to atmosphere regardless of pressure or that nothing changes doesn’t fit the pressure-driven flow. If outside pressure had fallen, the opposite would occur, with air moving outward and the seals breathing out.