The purpose of this document is to provide a comprehensive procedure for the implementation, validation and auditing of continuous measurement systems for carbon dioxide (CO2), in order to avoid exposing occupants to indoor environments with medium and high values of this gas. The concentration of CO2 in spaces with exclusively human occupation can serve as an indirect indicator of the accumulation of bioeffluents, as well as a reference value to adequately adjust the ventilation rate at all times. With the establishment of CO2 thresholds, it is intended to reduce both the negative effects of this gas on health and its impact on cognitive performance, in addition to reducing the risk of transmission of airborne diseases by bio-aerosols. This document is applicable to buildings for collective use, encompassing administrative, commercial, educational and public uses.