<p>This study thoroughly examined indoor air quality in six chain stores in Isfahan, Iran and involved the measurement of air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, CO₂, bacteria and fungi), alongside noise levels and thermal comfort over four seasons (2023–2024). To address the diversity of pollutants and enhance decision-making, an indoor air quality index (IAQI) was proposed, based on the importance coefficient and pollutant duration of presence. The results revealed that concentration of PMs in the autumn was relatively higher than in other seasons, with a strong correlation (R² = 0.926) observed between PM_2.5 and PM₁₀. For other parameters, levels remained within acceptable limits; however, noise levels in all seasons and stores exceeded standards. Airborne bacteria (312-1,007 CFU/m³), dominated by <i>Rhodococcus</i> and <i>Micrococcus</i>, and airborne fungi (639-1,332 CFU/m³), mainly represented by <i>Aspergillus</i> and <i>Penicillium</i>, were detected. Overall, most stores exhibited intermediate biological contamination levels across all seasons. The proposed IAQI for all seasons and stores, with some allowance for variability, falls into class D, corresponding to an intermediate/acceptable indoor air quality level. In conclusion, the air quality in studied stores does not pose an immediate concern for customers and visitors, continuous monitoring and the implementation of ventilation equipment are recommended to ensure the well-being of store personnel.</p>