Hello Mauhin. We have had 6 Vario-vent units in operation since December 2016. The following: For 4 of them, the sensors have been defective for 3 months, for one (the 5th) the entire electronics are defective. Additionally, the WLAN was defective in one unit, and furthermore, the hotspot was already defective. Massive moisture also destroyed the drywall in the interior of 2 units. The filters were always cleaned in a timely manner. The installer has now installed the Vario-vent units a bit more slanted, i.e. "squeezed" with more external slope in the mounting pipe; now it seems as if the condensate water sometimes drains outward. Inside, attempts have already been made by the manufacturer and the installer to seal with adhesive tape, but this tape is now coming off. Our apartment building is a block consisting of 10 apartments and EVERY apartment has problems. The manufacturer is extremely "unprofessional," appointments are promised and canceled, callbacks one can only dream of... The last work by the manufacturer was shutting off the guest WC due to an electronics defect with the comment "It's just a guest WC anyway," and "We will call you next week for a new appointment," that was 5 weeks ago!! Now an expert is coming next week because I refused to let the devices be manipulated further before clarifying what the cause of this almost complete failure is. Evidence in the form of photos and emails are of course available, a story of suffering for more than 16 months! Regards: René