It is recommended to run an ozone generator in a car for at least 30 minutes, up to two hours. During that time, the ozone gas will work to break down odors and bacteria molecules and eradicate them from the air circulating in your car. It is important to keep the windows closed during this process so the ozone is contained, along with everyone inside the car. After running the ozone generator for your designated amount of time, turn it off and open the windows and doors to let fresh air pass through your car.