Since the quality of ink jet prints, especially in the photographic sector has reached a high level, the gas fading of dyes has become an important issue. Up to now, a standardized test method for gas fading has not existed.Since it is believed that ozone has the most impact on gas fading phenomena, a testing system was developed which studies the effect of ozone exposure on ink jet prints.Humidity plays a significant role in the fading effects of ozone. Because of this, it is very important to guarantee a constant humidity level during testing.This contribution will describe state-of-the-art ozone testing, as well as rank the performance of several dyes of differing chemical structures. Some explanations of the mechanism of color fading will be discussed.