I bought this a month ago and I am glad that I did. Every time I burn an incense, the filter even in other room turns red so it seems very sensitive to dust, smoke etc. It probably also filters pollen as described (that I am allergic to), however if the windows are open and allergens are high, the filter does not turn yellow or red so not sure if it is very sensitive to pollen unless the air outside has smoke or has low air quality. The air feels fresh and clean though so definitely worth a buy!