The Air Sensor Kit excludes air and safeguards uninterrupted flow and fluid continuity when running ÄKTApurifier. The UNICORN controlled air sensor detects air in the system, and pauses the purification run. It therefore prevents column damage caused by air and ensures that the sample is completely injected. The air sensors are used together with the UNICORN WATCH programming function to increase control over programmed events. Variable sample volumes can therefore be applied with no risk of air entering the system or leaving valuable sample behind. If air is detected, and the procedure is paused, preventing air from being introduced to the column and ensuring that the sample is completely injected. The system can safely be run overnight.