Outdoor atmospheric chemistry and air quality have been the topic of research that intensified in earnest around the mid-20th century, while indoor air quality research has only been a key focus of chemical researchers over the last 30 years. Examining practices and approaches employed in the outdoor atmospheric chemistry research enterprise provides an additional viewpoint from which we can chart new paths to increase scientific understanding of indoor chemistry. This chapter explores our understanding of primary chemical sources, homogeneous and multiphase reactivity, gas-surface partitioning, and the coupling between the chemistry and dynamics of indoor air through the lens of outdoor atmospheric chemistry. The means to mitigate degraded air quality outdoors are heavily rooted in public policy actions, while the commercial sector mainly promulgates solutions for indoor air quality, making practical and actionable outcomes to research essential for prompt improvements to indoor environments. Indoor and outdoor environments have many important scientific distinctions, but a shared vision for healthy environments motivates both research communities in the same way
