Hemodialysis system including on-line dialysate generation

A hemodialysis system comprising:

• an on-line dialysate generator;
• a dialysate pump actuator configured to pump dialysate generated by the generator to a dialyzer;
• a conductivity sensor located adjacent to a temperature sensor upstream of the dialyzer;
• a blood pump actuator;
• an air detector;
• and
• a disposable cassette configured to carry dialysate pumped by the dialysate pump actuator, the disposable cassette including a combined conductivity and temperature sensor portion separate from and located so as to operate with the conductivity sensor and the temperature sensor, respectively, the combined conductivity and temperature sensor portion including a fluid chamber, the disposable cassette further configured to carry blood pumped by the blood pump actuator and to provide an air detection portion located to operate with the air detector.