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The lenses with two lenses seperated are thermal lenses. They're designed not to fog. Something must be wrong with your friends, like some water got in between the lenses or soemthing. Mostly, the single lenses fog more because there is only one pane of plastic stuff seperating the cold air from the warm air thats inside the mask.
The double paned masks have a neutral layer of air inside, and help so that nothing condensates inside.
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