I bought the air purification kit for the A5905 heater several years ago and use the heater exclusively in our bedroom and the purifier as needed. I had to replace the PCO component when the bulb died after several years of use. We did notice the difference when it wasn't used. I just ordered another unit and installed it in a second heater for our grandson's bedroom. Having heat and air purification in one unit is great. For me, the price, ease of installation, fast delivery and better air quality deserves a 5 star rating all day long.