The indoor air quality (IAQ) in micro-environments is extremely important due to its impact on health and productivity of students. This study presents the findings of indoor air quality (IAQ) investigations in engineering campus library at the University Sains Malaysia. Four levels of the library were investigated during May 2015. Measurements were carried out by using electrochemical analyzer and hand-held particulate matter (PM) instrument. The results showed that Formaldehyde, carbon monoxide (CO), Ozone, and total volatile organic compounds (TVOC) levels were found below Malaysian guideline values. Temperature ranged between 18.9–28.4 °C and relative humidity (RH) ranged between 49%–73% with an average of 62.2%. The indoor concentration PM2.5 level was 5.73±4.93μg/m3. All the monitoring pollutants’ levels were found below Malaysian guideline values in the ground floor, and the 1st and 2nd floors. However, several exceedances occurred in the 3rd floor. Inadequate introduction and/or distribution of fresh air may be the main problem in the left side of the building and in the 3rd floor. Thus, evaluation of the HVAC (Heating, Ventilation, and Air Conditioning) system should be examined