As a hermetic divide between exterior and interior atmospheres, architecture has been sealing itself off from fluctuating environments through its reliance on artificial breathing. The ability to induce and simulate a breathable environment allows architecture to be detached from nature as a separate entity. This condition needs to be re-conceptualized in order to address the over-reliance on mechanical systems through a study of biological respiratory systems. Therefore, the urban environment must evolve, challenging the divisive barrier of buildings to transform cities into an urban respiratory system, capable of purifying the atmosphere at both micro and macro levels. Urban sustainability therefore needs to challenge the static seal of buildings and learn to breathe from nature in order to become active urban respiratory systems, capable of purifying the atmosphere and contributing positively back into the urban fabric.