Ozone machines pose a greater safety risk to humans and cars than other odor removal methods. People or pets should never be in close proximity to an ozone generator, and the amount of time the machine runs should be carefully calculated. Smaller ozone generators may need to operate for an hour or two inside a car, while large ozone generators might achieve the same results in a matter of minutes. One important thing to consider is that extended and repeated use of an ozone generator can degrade the materials inside a car.