This study investigated experimentally the concentration of indoor air pollutants such as particulate matter (PM10), respirable particulate matter (PM2.5), volatile organic compounds (VOCs), carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxide (NOx), and sulfur oxide (SOx) in selected residential buildings located in the institutional, residential, commercial, and industrial areas of Aligarh city in Uttar Pradesh, India. To provide a more comprehensive picture of exposure risk, the building was selected to encompass locations with varying urbanization and traffic density characteristics. All contaminants were assessed using a portable indoor air quality sensor called "The Air Genius" in June 2024 (summer). Results indicate that PM2.5 concentrations exceed the CPCB threshold of 60 μg/m3 in all building units and measured sites. PM10 concentrations are above the allowed limit (100 μg/m3) in all building units except in bedrooms at all five locations. SOx, NOx, and CO2 concentrations are within the permissible limit at all units and locations (80 μg/m3, 80 μg/m3, and 1000 μg/m3, respectively). Carbon monoxide concentration is zero at all measured locations. The minimal average concentration of VOCs was discovered to be 4, while the greatest average concentration was 11.