TY - EJOU AU - Zhao, Chuhan AU - Morsli, Souad AU - Caramelle, Laurent AU - Ganaoui, Mohammed El TI - Ventilation Velocity vs. Airborne Infection Risk: A Combined CFD and Field Study of CO₂ and Viral Aerosols T2 - Fluid Dynamics \& Materials Processing PY - 2025 VL - 21 IS - 8 SN - 1555-2578 AB - Carbon dioxide (CO₂) is often monitored as a convenient yardstick for indoor air safety, yet its ability to stand in for pathogen-laden aerosols has never been settled. To probe the question, we reproduced an open-plan office at full scale (7.2 m 5.2 m 2.8 m) and introduced a breathing plume that carried 4% CO₂, together with a polydisperse aerosol spanning 0.5–10 m (1320 particles s⁻¹). Inlet air was supplied at 0.7, 1.4, and 2.1 m s⁻¹, and the resulting fields were simulated with a Realisable – RANS model coupled to Lagrangian particle tracking. Nine strategically placed probes provided validation; the calibrated solution deviated from the experiment by 58 ppm for CO₂ (8.1% RMSE) and 0.008 m s⁻¹ for velocity (15.7% RMSE). Despite this agreement, gas and particles behaved in sharply different ways. Room-averaged CO₂ varied by <15%, whereas the aerosol mass rose to almost three-fold the background within slow-moving corner vortices. Sub-micron particles stayed aloft along streamlines, while those 5 m peeled away and settled on nearby surfaces. The divergence shows that neither the CO₂ level nor the mean age of air, taken in isolation, delineates all high-exposure zones. We therefore recommend that ventilation design be informed by a composite diagnosis that couples gas data, size-resolved particle measurements, and rapid CFD appraisal. KW - Indoor Air Quality (IAQ); pollutants; CFD (Computational Fluid Dynamics); CO₂ Distribution; ventilation strategies; virus aerosol; air age DO - 10.32604/fdmp.2025.068093