Fire Safety Science Digital Archive

The burning process of fibers composing filter paper was examined during downward flame spread over a filter paper sheet, using microscopic photography, and progress of pyrolysis was visualized . During the period of flame passing, the color of fibers were observed to turn first into yellow, then into black. In an earlier stage, a few fibers at irregular intervals started to blacken and the numbers of blackening fibers increased. After all fibers blackened, the diameters and lengths of fibers started to decrease. The decreasing of lengths resulted in shrinkage of the paper sheet. This shrinkage was measured, and it was found that the length of fibers decreased gradually. The ratio of the volume of char to that of fibers before charring was measured and it was shown.that this ratio for thick paper sheet is larger than that for thin one. In this study, it was revealed that the pyrolysis proceeds in a heterogeneous way, and pyrolysis process of such fibrous materials is different from that of homogeneous ones. Consequently the heterogeneous structure of the materials must be taken into consideration for explaining detailed frame spread mechanisms.