Occupant-distribution-based CO₂ measurement for demand-responsive ventilation rate design in an office space

Department of Architecture and Building Science, Graduate School of Engineering, Tohoku University, Japan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Demand-controlled ventilation (DCV) in office buildings relies on a single zone-level carbon dioxide (CO₂) sensor to regulate outdoor air supply in response to zone occupancy inferred from CO₂ levels. Although effective for reducing ventilation energy relative to constant-volume systems, this strategy assumes spatially uniform occupancy and CO₂ distribution, which can limit both indoor air quality (IAQ) and operational flexibility. To address this gap, this study proposes a method that combines CO₂ sensing with seat-level occupancy detection to allocate ventilation air more intelligently across the breathing zones of occupants. In the experimental setup, CO2 sensors were installed in the breathing zone of each defined zone within a typical office layout and above the multi-user activity table to capture spatial variations in occupant-generated CO₂ concentration. Seat-level occupancy and CO₂ measurements were applied to simulate the ventilation rates required for occupied areas without implementing active control. System performance was evaluated by analyzing the modeled airflow response and IAQ maintenance under time-varying occupancy conditions. The results demonstrate that incorporating seat-level occupancy with CO₂ sensing can contribute to improving the responsiveness and efficiency of the building ventilation system.