The digital print industry is working toward the goal of adopting improved test methods for image permanence. One underlying assumption typically made in such testing is that the test chamber is providing consistent results for each sample regardless of where it is located or mounted. This study evaluated the uniformity of two Xenon test chambers and two ozone test chambers. Variation in the Xenon chambers was found to be much greater than in the ozone chambers. Moreover, unexpected responses, unique for each ink colorant, were seen in the Xenon chambers.