In recent years, a number of scholars—the likes of Emanuele Coccia, Eva Horn, Luce Irigaray, Peter Sloterdijk—have attempted to bring the air we breathe and inhabit into focus within the western philosophical framework, in disciplines from evolutionary biology to climate studies. This book project seeks to do something similar in the field of modern architecture. Notions of ventilation have concerned architecture since its beginnings, and architectural theory at least since Vitruvius has been preoccupied with the movement of air. Yet seldom does this discourse include the bodily process of breathing; instead, it addresses the replacement of stale air with fresh air by virtue of natural or mechanical means in buildings and cities. But is not architecture conceived for living beings in the first place? If ventilation is of any importance, it is largely because of the workings of our lungs, and ultimately, because our cells call for oxygen. Breathing is synonymous with life. Because it is vital, it is controlled by the autonomic nervous system and cannot be wilfully overridden. It takes place unconsciously—most of the time. From the mid-nineteenth century onwards, attitudes toward breathing changed significantly. Breathing became a widely exercised and discussed cultural phenomenon, often performed as a conscious act with increased pulmonary awareness. This project offers a wide-ranging analysis of pneumatic phenomena in modern culture, and by looking at specific structures, it throws into sharp relief the ways in which this new awareness for breathing inflected modern architecture.