[Cost evaluation of a ventilation system for operating theatre: an ultraclean design versus a conventional one]. 
The postoperative infection has been recognized as a critical problem in healthcare, increasing patients'complications and hospitalization costs.  At the moment the scientific evidence clearly linking ventilation parameters, such as air changes per hour, bacterial counts and infection, is lacking, with the exception of prosthetic joint surgery.  This study aims to evaluate the building and operating costs of an ultraclean system versus a conventional one (which satisfies the minimum performance requested by rules), also considering the debating efficacy of ultraclean ventilation on prevention of postoperative infection.  The results of our study show an increase of 24% in the building costs and of 34% in the annual operating costs for the ultraclean system versus the conventional one.  The estimated 24% increase of the building costs for the ultraclean ventilation system represents only a 5% increase if compared to the total cost of a not equipped operating theatre.  Therefore, the increase on costs linked to the use of high performance ventilation facilities seems to be so small that overcoming current rules towards ultraclean systems could be acceptable.