All the more reason to provide ventilation, while at the same time maintaining the security of having the garage door closed. I'd want screens, to prevent bugs, but they lakely aren't there because screen actually block more than 30-40% of the vent capacity of any opening. (That's why firefighters also remove the screens when venting a window.)
2014 RAM 2500 Laramie 4x4 Quad Cab w/Cummins Turbo Diesel, 2009 Rockwood 2607, and 3 'yaks!
300W of Suntech Solar, a Rogue MPT-3024 Controller, and a Xantrex PW2000 Inverter