Problem statement:The air quality study of PPR Taman Wahyu II, Selayang, Selangor was a residential project that was built on the former landfill site. The landfill site will produce landfill gases which can influence the air quality level in and outside the building. Approach: This air quality study also involving PPR Intan Baiduri, Batu Caves, Selangor as a control building. The air quality parameters chosen were physical, chemical and biological. Instruments used were HVS, Biogas Analyzer, Aeroqual, MultiRAE, ICP-MS, NMAM 7303 and gravimetric method. Gilian High Volume Air Sampler was used to measure heavy metal parameters that were conducted for 8 h, Personal Sampling Pump to measure total suspended particulates for 8 h, MultiRAE for H 2 S and CH 4 gas, Aeroqual for CO 2 gas, Multilog for CO gas and a Tedlar bag for O 2 gas. For biological parameters, settle plate method was used and conducted for 20 min. Veloci CALC and wind probe were used to measure physical parameters. Results: In the ambient air, the mean concentration of Total Suspended Particulate (TSP), lead and cadmium were higher at an exposed location compared to the control with a reading of 0.325±0.29, 0.108±0.050 and 0.06±0.045 ng m −3 respectively. The reason was that the exposed location was a former landfill site and there were several co-founding factors. Mean concentration for chemical parameters were higher at the exposed location and all the chemical parameters were not exceeding the EPA Protocol Gas for Single Component. The mean concentration of oxygen is 20.95±0.005%, carbon dioxide 669.25±84.109 ppm and carbon monoxide 1.8±0.957 ppm. For biological parameters, mean for the colony total count also higher at the exposed location compared to control location where the mean for bacterial was 17.75±4.573cfu while for fungal, the mean is 8.0±2.828 cfu. Indoor air quality results showed that concentration means of CO 2 was 877.8±59.40 ppm, CO was 5.0±0.89 ppm and O 2 was 20.9±0.05%. The concentration means for Cd was 0.3±0.26 ng m , bacteria was 38±16 cfu and fungal was 11±7 cfu. Conclusion: The concentration mean of the gas parameters had fulfilled the guideline standard. The statistical analysis revealed that there were significant differences between CO 2 , O 2 , bacterial, fungal and TSP between research building and control building. Research also showed that there is no differentiation between former landfill ambient air and control ambient air quality.