High Altitude Venus Operational Concept.
At 55 km altitude, the atmosphere of Venus is 27 °C and 0.5 bar (50 kPa), the equivalent pressure at an elevation of about 5500 m on Earth.
However, due to the large amount of CO2, the density for a given pressure is greater than in Earth's atmosphere.
Therefore breathable air acts as a buoyant gas.
At the same time, the gravity at the proposed altitude is 8.73 m/s2 versus 9.81 m/s2 on Earth's surface.