Buildings are expected to provide healthy and comfortable indoor environmental conditions for their users. Such conditions have diverse dimensions, including thermal, visual, air quality, auditory, and olfactory aspects. Indoor environmental quality standards, guidelines, and codes typically inform professionals in the building design and operation phase in view of procedural, contractual, and legal boundary conditions. Given this critical role of standards, it seems significant to examine the applicability and scientific validity on a regular basis. In this context, the present paper focuses on the standard-based definition of indoor air quality (IAQ) indicators and their respective values. Hence, the main aim of this effort is to study several common national and international IAQ standards in view of the scope to which they include direct or indirect evidence for the validity and applicability of their mandates and requirements. To this end, selected IAQ standards were assessed via a structured schema that includes not only basic information, quality indicators, and suggested and recommended value ranges, but also any reference to scientific studies. The findings of this effort identify certain issues with the transparency of the chain of evidence from the results of technical literature and standard-based IAQ recommendations. Moreover, recommendations are made for the development of future transparent and evidence-based IAQ standards and guidelines.