Indoor air comprises a mixture of many microorganisms, like bacteria, fungi and viruses, and this impacts human health unknowingly to them. This study focused on two crowded environments in Owerri, Imo State: school classrooms and public transport hub. Our aim was to collect and study airborne microorganisms, and the amount that were present in these environments. To test the microbial aspect of this prediction, we exposed Nutrient Agar and Sabouraud Dextrose Agar plates to the indoor air. Microbes were collected at different times of the day, and factors such as crowd density, ventilation and cleaning schedule affect what we found.  Our result showed that classrooms with open windows had a higher presence of environmental bacteria such as, Bacillus, Pseudomonas, ranging from 996 – 6889 Cfu/m3 and fungi like Mucor, Aspergillus and Penicillium ranging from 1448 – 3422 Cfu/m3. On the other hand, human-associated bacteria such as Staphylococcus and Cutibacterium found on human skin and respiratory droplets, were isolated from the sample from crowded public buses with a range of 897 – 3868 Cfu/m3.  Microbes found in indoor air appeared to be largely affected by ventilation, though regular cleaning seemed to reduce surface contamination. Spaces with good airflow had more varied, balanced microbial communities, while poorly ventilated spaces showed higher levels of potentially opportunistic microbes. This study showed that proper ventilation, and reduced overcrowding makes indoor environments healthy. Proper understanding of these differences will help in making good decisions when building and maintaining public spaces, with clear implications for indoor public health management.