I bought it when we had a newborn baby and suddenly the African dust came to Crete. We are not smokers and we ventilate the house daily, so the environment is generally clean. However, it works and does a good job because it detects the use of an electronic cigarette (which does not have pollutants like tobacco) and operates automatically. When activated due to pollution detection, it is somewhat noisy (like a kitchen hood), so in my case (small disturbance) I prefer to have it constantly in sleep mode, which is 100% silent. After 6 months, the time came to replace the filter and I had it deactivated for 11 days, then I realized the difference it brought to the house as I started to see dust on the tables even on the same day after cleaning, while as long as the device was working, I never saw anything similar. Finally, when I changed the filter, it needed internal cleaning with an electric vacuum cleaner because there was dust left, as well as on the sensor on the back side.