Abstract: A bubble trap for an extracorporeal blood handling or other fluid handling system has a chamber (10) constructed from a top section (20) and bottom section (30). There is a fluid inlet (50), gas vent port (70) for purging gas that has separated from the fluid in the chamber, and a fluid outlet (50). There are two balls (64) and (74), which act as check valves to prevent fluid flowing out the vent port, and gas escaping through the fluid outlet. The chamber geometry prevents entrapment of either ball in the corner as blood level rises or falls. Squeeze bulbs (66) and (76), and shutoff valves (68) and (78), provide for unseating the check balls.