Designed to create a comfortable environment for people who suffer from pet allergies and dust pollen. The filter effectively retains particles leaving your room and the ambient air hygienically clean. The innovative Timestrip® indicates when the filter needs to be replaced. To activate the TimeStrip®, press on the green arrow. A red fluid starts to creep from left to right of the strip over a period of approximately one year. Once the fluid has reached the far end of the strip and the bar has changed completely to red, the word ‘Replace' will appear, indicating that a new filter should be fitted. Suitable for S2000, S300, S400, S500, S600, S700, S800 and S7000 upright and Classic C1, Dynamic U1.