Drawing on debates about health and space in science and technology studies, anthropology, and geography, the chapter develops an analytical framework of enclosure/volume to interrogate how air and breathing spaces are conceptualized, materialized, and negotiated in situated practices. It explores the limits of enclosure-based approaches that individualize protection (e.g., through masks, filters, or private purification systems) and instead advances the idea of shared atmospheres. This shift foregrounds air as a collective condition through which social and ecological relations are constituted and contested. Empirically, the chapter examines clean air policy and urban planning documents in the UK relating to interventions that seek to construct and support healthy atmospheres. It traces how these interventions approach air as socio-technical and mediating relations between communities, infrastructures, and governance systems. Through examples such as School Streets, healthcare advocacy, and participatory air-sensing initiatives, the analysis shows how volumetric and relational approaches to air can challenge the epistemologies and practices of enclosure that dominate environmental management. It considers interventions as possibilities for commoning atmospheres by elaborating how they foster responses that extend beyond individual health to support policymaking and planning aimed at addressing broader social and environmental injustices. Emerging in variegated, incremental, and often improvised ways, these interventions resist the impulse to eliminate risk through privatized enclosure, offering instead a dynamic rendering of space as volume that attends to the inclusions, exclusions, and tensions of enclosure. The chapter argues for policies and infrastructures that cultivate shared social practices and collective responsibilities in the pursuit of healthy air and atmospheres.