The NEW Scott fan, and the 509 fan are both made by HaberVision.
Haber owns the patent and produces them. They are re-labelled with other manufacture's names.
The HaberVision design is that way for a reason. What makes it unique is that the fan is not always on or always off. Always on will dry out your eyes. Always off, well that is self explanatory. The HaberVision Eliminator fan has a built in humidty sensor. When humidity levels go up, the fan turns itself on BEFORE fogging and prevents it. Back off when the humidity levels drop down to normal levels. The Haber design also pushes air out, some other brands pull air in. Constant air coming in on the always on designs will cause fogging issues. IF you open the goggles up and off your face on a cold day you will thermal shock the lens. That alone will cause fogging. There is a reason we use a double lens in the winter and that is because the air pocket between the inner lens and the outer acts as an insulating layer between your warm face and cold exterior, preventing thermal shock.
It is correct that if you form an ice layer over the foam the fan won't work properly but a simple sweep with your hand/finger will clear that off. Our motors operate the same way. Plug the air intake and they don't breath.
The fan is not designed to prevent fogging when you are moving, you have good air flow coming to your face and don't need a fan. When you stop is when the Haber fan is designed to prevent fogging. When you stop you don't have airflow coming to your face. Most guys pull off their goggles when they stop. This works but it also introduces cold air to the inner goggle lens, causing fogging. Also each time you take the goggles off and on, you increase the chances of getting snow or water on the inside face, once again... causing even more fogging issues. If you leave the goggles on your face when you stop, you won't get snow or water on the inside, if you can prevent that you will have FAR FAR less fogging issues. Let the Eliminator keep you fog free when stopped.
