The previous paper (Part 1) proposed the concept of "equivalent material age" that uses the Arrhenius relation and explained a method for long-term prediction of indoor volatile organic compound (VOC) concentration considering temperature dependence. This paper first describes the experiment conducted to validate the long-term concentration formula and the results of the experiment and reports on a comparison of the measured values obtained with the predicted values. The experiment was conducted by a method conforming to JIS A1901:2003. The material measured was formaldehyde. In the experiment, measurement was made in five cases involving different conditions. The measured changes over time in the emission factor obtained in the experiment in which temperature was varied over time tended to agree fairly with the predicted values, but differences began to appear at a certain point in the experiment. A likely reason for the occurrence of the differences was the influence of differences between individual materials (members). It is thought that if prediction accuracy is to be improved, it is necessary to use more than one test specimen for each experiment. The authors intend to investigate the influence of differences among individual specimens in order to enhance prediction accuracy.