Fogging is caused by the moisture in the air on the inside of your mask cooling against the lens when there is a significant difference in the temperatures between the inside and outside.
In order to reduce fogging you need to prevent moisture from sweat and your breath from getting inside the eye cavity or increase ventilation. When you are outside in the woods sweating that can be very difficult to do.
Things you can do to help stop fogging:
- Use a thermal or dual layer lens. This creates a barrier between the outside and inside of your lens.
- Use anti fog spray or coating on the lens. This prevents the moisture from sticking to the lens.
- Use a goggle ventilation fan.
- Make sure you have a good seal to prevent your breath from getting into the eye cavity.
- Keep the mask as dry as possible and use a headband to soak sweat before it gets into the eye cavity.