Methods and systems for a heating, ventilation, and air-conditioning (HVAC) system for an enclosed environment may be configured to at least one of heat and cool air and include an air circulation system configured to circulate air at least within the enclosed environment. The air within the enclosed environment may comprise at least the indoor air. The system may further include an outdoor air inlet for introducing at least a portion of outdoor air into the enclosed environment, where the outdoor air comprises air from outside the enclosed environment. The system may further include a scrubbing system having an adsorbent material to reduce presence of at least one gas contaminant in the indoor air. A controller system may be included for controlling the operation of at least one of the circulation system and the scrubbing system.