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To assess occupant thermal comfort, field studies were carried out in naturally ventilated (NV) classrooms of Indian Institute of Technology Kharagpur. The location has a hot–humid climate. Surveys were taken during both semesters over the academic year 2013–14. Results of the surveys gave a regression neutral temperature near 29 °C while preferred temperature was found to be 26.8 °C. Using student responses to thermal acceptability question, 80% occupant satisfaction was found between 22.1 and 31.5 °C operative temperature. Over the survey duration, nearly 79% of responses accepted their thermal environment. Analysis of thermal preference and thermal acceptability votes showed a distinct preference amongst occupants for cooler than neutral sensation. Diurnal variation of temperature that would be acceptable to 80% or more occupants was found to be a 4 °C wide band. Study of student actions during surveys showed that fans were brought into play more often than windows. Variation of clothing showed strongest correlation with the day's minimum temperature. Overall, observations from the study showed broad comfort zones and significant level of occupant adaptation to the environment of NV classrooms.