Keep the defroster vents unobstructed so hot air can succeed in the windshield calmly, cutting fogging and ice formation.

https://marvelvsdc.faith/wiki/Clean_Vision_In_Front_The_Importance_of_Windshield_Substitution

Keep the defroster vents unobstructed so warm air can succeed in the windshield lightly, cutting fogging and ice formation.