Cleaning of ventilation ducts in ventilation systems

Why a crazy idea? Explain to me what is wrong with clean air?

Sorry, but you have no expertise and you entangle yourself in contradictions. Also, the statement that from 2019 according to an EU directive only passive houses must be built is complete nonsense. I'm out of here.

Sorry, but I wouldn’t entrust you with my system if you can’t even correctly explain the basics of a ventilation system... A crossflow heat exchanger definitely does not mix exhaust air with supply air. The heat and moisture transfer in an enthalpy exchanger takes place across a surface/membrane that does not allow air to pass through. Otherwise, the whole purpose of such a system would be lost. The minimal dust in the supply air ducts does not come from mixed exhaust air but because even the best commercially available filter for ventilation units lets a little through. This is not a cleanroom system in an industrial standard.

Sorry, but you have no expertise and are contradicting yourself.
Also, the statement that from 2019 onwards, according to the EU directive, only passive houses must be built is complete nonsense.
I'm out of here.

I have to strike out "must", that is wrong, "should" is the correct term. You can look that up on Google.

What matters to me is clean air in houses with ventilation systems. That is what I am trying to find out here: what people are willing to do with such systems so that the system continues to operate cleanly.

A radiator in winter is just a heat exchanger with your living space. Always this constant contamination of the living space with the dirty heating water... oh wait, no! Exactly zero dust comes from the exhaust air into the fresh air.

Mit geht es um saubere Luft in Häusern mit Lüftungsanlagen. Das ist es was ich hier versuche herauszufinden was die Menschen mit solchen Anlagen bereit werden zu machen das die Anlage weiter sauber läuft.

First of all, they will ask themselves whether it is even running unclean. You find everything on Google – including false stuff. And what is in the pipes is by no means in the room air.

The passive house standard is to apply to new buildings from 1.1.2021, if the Energy Saving Ordinance 2020 is adopted as planned. Everything is still open.

The supply air filter is dirty, which is logical
The exhaust air filter hardly has anything.
No visible dirt on the heat exchanger so far
Summer cassette spotless
No dirt visible on the supply or exhaust air ducts installed in the house.
So far, I see no need to clean the air system

I installed my system myself, for example, so I am not an isolated case.

Exactly, anyone who goes to the trouble of installing such a system themselves will not have someone come to clean it for 600€+. They know where and how to open and clean their self-installed system.

But by the way: when you installed your system yourself, didn’t you take a closer look at the heat exchanger? Or at least read the technical description? I always think it’s good when someone wants to build a second, independent source of income. That kind of thing should be supported. BUT: the first step is always: find someone who knows their stuff. Legally, tax-wise, technically, marketing-wise, etc. With this thread here, you’ve already scared off more potential customers than you’ve gained. That’s avoidable. You don’t know how an air-to-air heat exchanger works, but you want to clean it? Sorry, customers notice that very quickly too and will kick you out faster than you can blink.