Product review (4 stars): a requirement for the venta airwasher
The Venta manual indicates this liquid is necessary for proper evaporation from the Airwasher (it makes the water sheet across the gaps in the wheels), and that seems to be true.  I ran my airwasher with plain water (rinsed out), and a nearby humidity sensor showed 30-31% even after extended operation.  After changing out the water and adding a dose of the treatment, the humidity sensor's reading rapidly moved up to 40-42%.

The liquid is also recommended to prevent mineral (and bacteria?) buildup in the Airwasher. It's largely odorless, and the label states it contains: water, quaternary ammonium chlorides, water softening agent

The label also states a 30 month shelf-life and 12 month expiration after opening. I'm not clear what in the ingredients will expire that rapidly, and it seems a little convenient to Venta's marketing for the bottle to expire in time for the next cold-weather season. There are markings on the side of the label indicating 10 "doses" of the contents.  At 10-14 days per dose, that works out to 4-5 months, plenty for winter in most of the US. There's actually enough extra liquid above and below the markings for another 1-2 doses, so it should go 5+ months easily.  Since I typically humidify only 3 months a year, a single bottle could last me most of 2 seasons (aside from the labeled shelf-life).

Unlike some older reviews, I got the 35oz bottle as pictured on this listing at this time.

I mark it down a star for the Venta requirement to use this somewhat pricey consumable, and the arbitrary shelf life.

Recommended, since it is required for proper Airwasher functionality.