Indoor air quality (IAQ) can be described as the quality of air weather inside or surrounding the buildings and structures
which are associated with the health and comfort ability of occupants in the buildings. The level of IAQ in buildings can be influenced
by microbial contaminants activities, chemicals exposure and allergens that seriously can create health effects to the building’s
occupants. In the present study, the effect of environmental factors such as temperature and relative humidity on the optimum growth
of Aspergillus niger (A. niger) was investigated. The study revealed that the optimal fungal growth of up 43mm in diameter was
evidenced under room temperature of 30oC at the end of a five day incubation period. However, the relative humidity from 40% to 90%
applied is able to support the growth of the A.niger. The relative humidity of 90% shows the optimal effect where 56 mm of diameter
growth happened after 5 days of incubation. The significant finding to emerge from this study is that environmental factors such as
temperature and relative humidity do affect the growth of A.niger. The optimal temperature and relative humidity for A.niger to grow
are 30oC and 90%, respectively.