I have the Miele C1 and after a few cleanings, once it collects a certain amount of dust inside the bag, the air exhaust starts to smell during operation. So I decided to upgrade the filter either to a HEPA or to the mentioned active air clean, but I didn't know which one. I sent 2 emails to the Greek representative asking for their recommendation for my case, but they didn't respond to any of them, which is unacceptable for a premium company. So I sent an email to the German representative where I received a response within a few hours and they recommended the active air clean.
Without hesitating, it slightly reduced the strong odor but didn't do anything special and the problem continued to be bothersome. I believe that the HEPA would be more effective in my case, but I haven't tried it yet. I will soon proceed with its purchase and evaluate it afterwards. This particular product is definitely not worth its price of 20+ euros in any case