Temples are a significant part of India’s cultural legacy, spanning from the northern to the southern regions, and harboring an extensive assemblage of deities. Many temples, dating back hundreds of years, remain well-preserved and serve as focal points for cultural activities. Ujjain, a historic city located on a plateau in the Malwa region of the Vindhyachal mountains in Madhya Pradesh, is home to the Mahakaleshwar Temple, a prominent religious site. However, the increasing number of worshipers has led to a decline in the temple’s indoor environmental quality (IEQ). This study aims to evaluate the indoor air quality (IAQ) and infection risk in the Mahakaleshwar Temple by analyzing ventilation rates and their impact on airborne transmission. Carbon dioxide was used as a tracer gas to calculate the air changes per hour (ACH), and the Wells-Riley model was employed to assess the relationship between ventilation rates and infection probabilities. The results highlight that insufficient natural ventilation and poor air circulation have led to discomfort among devotees, with reported issues such as suffocation, irritability, and nasal congestion. Elevated CO2 levels, reduced oxygen levels, and increased temperature and humidity have further worsened the indoor environment. The findings underscore the critical need for improved ventilation systems in high-occupancy religious buildings to mitigate health risks and enhance comfort for devotees.