The present invention consists of a blood reservoir that incorporates a separate chamber designed to trap condensing water vapor. The blood chamber and the vapor trap are in fluid communication along their top assuring that vacuum applied to the top of the vapor trap is equally applied to the blood chamber. The combination is also structured to prevent condensate water accumulating in the vapor trap chamber from overflowing into the blood chamber as well as provide a structure that allows the end user to empty the water in the vapor trap chamber.