This paper is the first one in a series of two papers presenting the main results obtained in a School Building, which are analyzed in view of the actual Indoor Air Quality (IAQ) Portuguese national regulation. Measurements were carried out in one building, ventilated by mechanical system to evaluate IAQ and thermal comfort parameters. Direct measurements were made with portable monitoring data loggers and in some longterm measurements. The students assessed through questionnaires the IEQ parameters felt in the classrooms a few moments before the end of the class. The IAQ and thermal comfort conditions in higher/university schools buildings has been found to be poor because of the high density of students in class rooms. In particular, the IAQ is a significant issue for these buildings in order to be healthy and comfortable for learning performance of students.