Carparks are constructed to provide a certain number of car spaces for visitors, shoppers and/or clients of a commercial facility. The required ventilation system design is generally based on local standards provided by local authorities. The purpose of the current study is to develop a performance based ventilation system for a shopping center carpark. The aim of the study is to undertake computational fluid dynamic (CFD) modelling of the carpark to determine the potential minimum ventilation exhaust rate levels. Results showed that the proposed carpark exhaust system was considered acceptable and no modifications were required. The CO concentration levels in all areas, except within the immediate vicinity of car exhaust plumes, were below 100 ppm. The average predicted CO rise was less than 25 ppm across the carpark which is in compliance with the current Worksafe Australia and WHO CO exposure limits. Moreover, results indicated that the 64,000 l/s exhaust air flowrate was sufficient, and could be reduced to 50,000 l/s. From a financial point of view, it was concluded that the removal of the outlet grilles located at the Southern wall of the Commuters section of the carpark was an acceptable alternative. This cost saving is based on the potential deletion of a fan system, plenum arrangement and shaft which are required as part of the deemed-to-satisfy system design. © 2017 by authors.