Abstract: The indoor air quality of a nitrogenous fertilizer company was assessed using high volume sampler, impingers and noetox gas monitor. The parameters determined were suspended particulate matter, ammonia and carbon monoxide. The results showed that the mean levels of suspended particulate matter varied from 216.8 ± 56.2 � 2,460.4µg/m3 at the study sites and 42.5�g/m3 at the control site. The mean values of ammonia ranged from 234.7 ± 193.9 -805.2 ± 53.9µg/m3 at the sites and 51.4 ± 4.2 µg/m3 at the control site. The mean values of Carbon dioxide varied between 1.07ppm ±0.71 and 4.65ppm ± 7.93. The differences between the mean values of suspended particulate matter and ammonia at the study sites and control (Training house) were significant (p < 0.05). The study showed that the levels of suspended particulate matter and ammonia at indoors of the selected sites present a health hazard, indicating that the factory workers are at high risk. The health impact of indoor pollution in the production areas of the company should therefore be closely monitored.