Carbon dioxide (CO ₂ ) is commonly used in the ventilation control of buildings as a metric for indoor air quality (IAQ); however, few commercially available sensors exist that can reliably measure CO ₂ while being low cost, exhibiting low power consumption, and being easily deployable for use in applications such as occupancy monitoring. This work presents an initial assessment of a chemiresistive CO ₂ sensor that leverages a polymer blend of branched polyethylenimine (PEI) and poly(ethylene glycol) (PEG) as the CO ₂ absorbing layer. Prototype sensors were assessed in a bench-top environmental test chamber at various ambient temperatures (22-26 °C), relative humidity levels (20-80%), and CO ₂ concentrations (400-2,000 ppm), which are typical of indoor environments. The results show that with some further advancements, the proposed method could serve as an alternative to current commercially available CO ₂ sensing technologies.