What is the function about ventilation of ski goggles?

Venitlation on ski goggles helps control the climate inside the snow goggle.

Every brand has different features to allow air to flow through the snowboard goggle to prevent moisture from building up inside which can minimize fogging. The greater the ventilation, the less likely your goggles will fog up.

1) Low-Minimal ventilation these goggles may have a tendency to fog when not moving.   

2)Medium Ventilation goggles prevent fogging during low-to-moderate activity.   

3)High Ventilation goggles give you the maximum amount of ventilation to prevent your skiing goggles from fogging.