The Tobii Pro Glasses 2 system is primarily designed for use in dry indoor environments. Depending on the level of sunlight Glasses 2 will function in outdoor environments as well. Make sure that the Glasses are not exposed to direct sunlight since that might affect eye tracking results negatively. Further make sure that the Glasses are protected from water or moisture since that might harm the unit. For more info please read chapter 1.1.11 of the Tobii Pro Glasses 2 Manual.