Indoor air quality (IAQ) has emerged as a critical public health concern in rapidly urbanizing cities like Lahore, Pakistan, where ambient pollution levels regularly exceed WHO safety thresholds during annual smog seasons. This study aims to quantify the independent and combined effects of indoor plants and natural ventilation on IAQ through a quasi-experimental design, with implications for affordable IAQ management in smog-affected urban contexts. Eight office spaces across Beaconhouse National University were monitored over three months (July–September) using Awair Element consumer-grade sensors measuring CO \(_2\) , PM \(_{2.5}\) , PM \(_{10}\) , and TVOCs at five-minute intervals. Six air-purifying plant species—Dracaena trifasciata, Aloe vera, Epipremnum aureum, Chlorophytum comosum, Rhapis excelsa, and Chamaedorea seifrizii—were deployed to assess remediation capacity under varying ventilation scenarios. Results showed that natural ventilation was highly effective, with windowed spaces exhibiting 96.2% lower PM \(_{2.5}\) (2 \(\mu \) g/m \(^3\) vs. 53 \(\mu \) g/m \(^3\) ) and 70.5% lower TVOCs (535 ppb vs. 1,814 ppb) compared to sealed rooms. Conversely, plants in non-ventilated spaces achieved substantial PM \(_{2.5}\) reductions (96.7%) but paradoxically increased TVOCs by 63.3%, likely due to human activity overwhelming plant metabolic capacity. Temporal analysis revealed that CAM plants effectively reduced nighttime pollutants when occupancy ceased, though daytime human activity in sealed offices generated pollutants faster than plants could metabolize them. These findings demonstrate that phytoremediation effectiveness critically depends on adequate ventilation and appropriate space-to-plant ratios. The study concludes that meaningful improvements in IAQ in Pakistani urban contexts require integrated strategies combining ventilation, strategic plant deployment, and effective policies on human presence in enclosed spaces, particularly during Lahore’s severe smog season.
