INTRODUCTION Recent advances in medical technology necessitate regular reevaluation of the heating@ ventilating and air-conditioning (HVAC) needs for hospitals facilities. The purpose of the HVAC system for an operating room is not only to achieve thermal comfort but also to remove airborne contamination. It is vital to perform the surgery in a particle-free environment and maintain the minimization of contamination. However@ little knowledge or quantitative information about energyefficient HVAC system is available on how to control the environmental variable in the operating room effectively. With cost of rising@ value of conservation grows. Since HVAC systems of operating room operate continuously@ it is vital and significant to consider energy-efficient strategies as well as to achieve an acceptable performance for contaminations contort. Recent research on operating room ventilation performance against airborne infection has been investigated thoroughly by Chow et al. (2005). They also reported that surgical site infection due to airborne bacteria is a key factor in developing the HVAC system in the operating room. Another comprehensive review on the air movement under infection control focus in operating room has been presented by Pereira et al. (2005). Their study also identified the control strategies which could reduce the risks of airborne contamination in operating infection. The airborne particles in the infection process and the microbiological control for the air distribution system have been analyzed extensively. Besides@ the experiment and modeling of airflow pattern as well as the diffusion of contaminants in an operating room was performed by Woolsey et al. (2004). Computational fluid dynamics (CFD) simulation technique is a well-known and widely-accepted scientific technique that allows improvement of airflow distribution for cleanroom configuration (Wang et al. 2009). They also identified some option under a limited budget@ as well as reduced trial-and-error effort when modifications of cleanrooms have to be conducted. Moreover@ the CFD codes were successfully used to simulate the air distribution and contamination decay as well as comparison of indoor particle concentration in different rooms (Zao and Zhang 2009). Besides@ the biological contaminant control strategies under different ventilation models in the hospital operating room have been proposed by using CFD simulation (Zhang et al. 2008). Results showed that improving air flow distribution could reduce particle deposition on certain critical surface. Furthermore@ the integrated effect of medical lamp position and diffuser discharge velocity on ventilation performance in an operating room has been investigated (Chow et al. 2006). The dispersion of infectious particles from both surgical team and patient were simulated through CFD analysis as well. Field-measurement is essential to assure the operating room performs correctly and achieves the contamination standards. The biological contamination control strategies under different models in operating room has been simulated and then compared with filed measurement@ to check the acceptable level of consistency (Zhang et al. 2008). Besides@ bioaerosol characteristics related to human dispersion were evaluated extensively based on field tests data in hospital cleanroom with different class levels (Li and Hou 2003). Furthermore@ particle counts and microbial counts during 105 operating procedures under laminar air flow condition were surveyed and investigated to assure the high air quality in operating room (Hansen et al. 2005). Some valuable information describing cleanroom measurement to evaluate the overall performance of cleanroom can be found in literature (IEST. 1993). General principles and methods on bio-contamination control of cleanroom are described extensively in the stand of ISO. 14698 (ISO 2003). Besides@ the essential information on design consideration@ equipments and comprehensive procedures for certified testing of cleanrooms were reported in NEBB (1996). Although much research has been done on CFD simulation as well as for field measurement for operating rooms@ little quantitative information is available on compromise of contamination control and energy saving potential. In this study@ the strategic approach on performance improvement of the HVAC system for an operating room will be investigated. Variable speed driven strategy was also performed to verify the potential of energy-saving opportunity under specified contamination standards. A physical partition curtain has been conducted auxiliary around the HEPA filter of an operating room to validate the improvement of air distribution and contamination control. Both numerical simulation and field measurement of a full-scale operating room will be carried out in a district hospital in Taiwan. The performance of contamination control could be evaluated comprehensively not only by airflow distribution but also concentration profile under different curtain length and different face velocity provided by inverter-driven fan unit. Besides@ the variation of temperature and humidity for the operating room will be monitored on site to evaluate the effect induced by reducing the face velocity of HEPA filters.