Ombraz can fog up. If you put them on and the lenses are cold, this is a recipe for foggage. Warm the lenses up in front of your car heater or inside your jacket before putting them on. If you have your Ombraz cranked too close to your brow, this can limit airflow which can also cause foggage. The sides of the glasses provide ample ventilation. If you're working hard, loosen them up slightly to add a bit more room between your brow and the frames. There are conditions which fogging up is hard to avoid, but we do everything possible to prevent it. If fogging is really bad, try applying an anti-fog coating to the lenses - available at REI.