The new FI negative ionisation cell has been designed and built for installation inside air treatment units, or along air distribution ducts. FI is a completely new development in air treatment, and its installation after an electrostatic or absolute high efficiency filtration system ensures better sterilisation and reduction of smells, together with better environmental comfort. Its multi-pole connection system means that several ionising cells can be connected at the same time, based on the air load and filtration requirements. Ionising cells are installed and removed by simply sliding them across the air treatment unit filter holder frame. The built-in electronic power input circuit is equipped with LEDs to notify the user that the filter is working correctly.