In the late 1980s, when engineers constructed Biosphere 2 in Oracle, Arizona, they created the most airtight ecological enclosure ever built. However, sealing over 7 million cubic feet of air beneath a glass geodesic superstructure created an immediate thermodynamic crisis. As the desert sun heated the sealed atmosphere each day, air temperature spiked, causing internal air pressure to rise sharply.
At night, the air cooled rapidly, creating a vacuum effect. Left unmitigated, these pressure differentials would have easily blown out the thousands of glass structural panels. To balance the atmospheric pressure without leaking gas, engineers built two massive variable-volume structures known as the lungs.
Each lung consists of a circular dynamic expansion chamber housing a synthetic rubber membrane attached to a 16-ton weighted aluminum disk suspended from dynamic pan-and-pin linkage systems. When solar heating expands internal air, the air is driven through underground tunnels into the lung, raising the weighted rubber diaphragm. As the facility cools, gravity pulls the heavy diaphragm down, pushing air back into the main structure.
This mechanical breathing system maintains atmospheric equilibrium within a fraction of a millibar without losing a single molecule of inner atmosphere.