The quality of the air in office buildings can impact the health of those working inside of building. Indoor air pollution can be a real concern because people can spend as much as 90% of their tinle indoors and have an immediate or long-term reaction to poor indoor air quality. Most people are aware that outdoor air pollution can significantly affect people's health, but pervious studies have shown that levels of air pollutants indoors may be anywhere from 2 to 5 times greater than outdoors, and in some cases more than 100 times greater. Indoor ventilation and air quality refers to the quality of the air and environment inside buildings, based on pollutant concentrations and conditions that can affect the health, comfort and performance of occupants -- including temperature, relative humidity, light, sound and other factors. Creating a better ventilation and indoor air quality can help building owners, managers, occupants, architects and builders to minimize or eliminate the negative health effects. In this study, indoor air quality of the office of Wind Engineering Research Center (WERC) at Tamkang University is simulated by computational fluid dynamic, the software of AirPak2.1.12. The results show the concentration distribution of the ozone in offices. The CFD simulations were determined to reduce ozone concentrations more effectively.