Interesting video but like all scientific tests, it needs to be repeatable. And maybe it is. I would assume the effect would vary with the person's face size and shape and helmet. And local wind speed at a stop. There is another factor. Inside the helmet unused volume and lung capacity. How much exhaled air is exhausted to the outside and how much new air is brought in when you inhale?
It would be fun to do this experiment, actually, although I suspect I would have no issues even though my LS2 Valients have curtains on their chin bars. But they do fit tight. When its cold, the main visor and bar would be down. But due to fog, at stops the main visor would be cracked. When its hot, I dont pull own the chin bar.
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