To contribute to the confinement safety evaluation of radioactive materials in a glove box (GB) fire accident, combustion tests with polymethyl methacrylate (PMMA) and polycarbonate (PC) as typical panel materials for the GB have been conducted with a relatively large-scale apparatus. As important data for evaluating confinement safety, the release ratio and the particle size distribution of soot generated from burned materials as source term data for analyzing the migration behavior of soot particles were obtained. Furthermore, the effect of soot loading on the rise of the different pressure (ΔP) of the high efficiency particulate air (HEPA) filter ΔP was also investigated. The results showed that the release ratio of the soot generated from the burned PC was about seven times as large as PMMA and the relatively large particles of the soot from PC were also larger than PMMA. In addition, by considering the effect of the loading volume of the soot particles in the relatively low loading region of the soot, it was found that the behavior of the rise of ΔP accompanied with soot loading could be represented uniformly regardless of the kinds of combustion materials.