There is a risk of air embolism during the preparation of the patient’s dialysis access and via the dialysis machine blood circuit. It is a serious event, with the symptoms and consequences depending on the site of passage of the air embolus within the circulation. It can lead to peripheral circulatory obstructions, convulsions, stroke or a cardiac event. The risk of air embolus is increased if the patient/nurse repeatedly silences an air alarm. during an air alarm both the venous and arterial machine line clamp close. Overriding these alarms re-opens the clamps allowing the blood flow and air to either flow backwards up the arterial line or past the venous aid chamber to the patient .