## 3 Experimental Results
### Effect of the Opening and Penetrant Size  
Figures 11-13 analyze the effects of the opening area, penetrant area (based on measured outer diameter), and actual solid cross-sectional area of the penetrant (outer diameter minus inner diameter) on peak temperature. The analysis distinguishes between nonmetallic and metallic pipes, and all dimensional values are based on actual measured areas derived from outer diameters. The focus was on comparing response patterns when one variable remained constant (either opening size or penetrant size) while the other varied. Figure 11 shows how the peak temperature changes with opening area. For nonmetallic pipes (Figure 11a), the peak temperature increased linearly with the opening area, maintaining high correlations. When exposed to high temperatures, nonmetallic pipes soften and collapse turning the entire opening into a heat-entry point; consequently, the heat-blocking performance of the firestop material is the determining factor in fire resistance. Thus, for nonmetallic pipes exposed to high temperatures, fire-resistance performance is more strongly influenced by the size of the opening to be sealed than by the size of the penetrant itself. However, in conditions where both opening size and penetrant size increase together, this statistical relationship may give the impression that the pipe's size has a greater influence. In practice, because nonmetallic pipes are destroyed by high temperatures and no longer function structurally, this cannot be interpreted as a structural contribution. Meanwhile, for metallic pipes (Figure 11b), the influence of opening area on performance was less significant, with lower correlation coefficients. Under conditions where the pipe diameter increased while the opening remained constant, the peak temperature rose, and the slope of the trendline gradually decreased. This indicates that metallic pipes, which maintain structural integrity, function as direct heat-transfer paths, and thus pipe diameter, rather than opening size, plays the more decisive role in determining fire resistance. Figure 12 shows the peak temperature as a function of the penetrant area (based on actual outer diameter). For nonmetallic pipes (Figure 12a), a high correlation was observed, however, this arises from the experimental linkage between the pipe and opening sizes. Because nonmetallic pipes disintegrate at high temperatures and no longer influence the heat-transfer structure, the size of the pipe itself has a minimal direct effect. In contrast, for metallic pipes (Figure 12b), while the correlation coefficient was lower, it reflects a more meaningful structural relationship. As the penetrant area increases, the heat-conduction path expands, and even under constant opening conditions, the peak temperature rises accordingly. Figure 13 analyzes the peak temperature as a function of the solid cross-sectional area of the penetrant. For nonmetallic pipes (Figure 13a), a high linear correlation was again observed, but--as with previous findings--this is caused by coupling with the opening size increases rather than any physical influence. In contrast, metallic pipes (Figure 13b) also showed a strong correlation with the penetrant solid area, confirming that as the outer diameter increases, the solid cross-section increases proportionally, expanding the heat-transfer path and causing an increase in the peak temperature. Figure 11: Peak temperature as a function of opening area: (**a**) nonmetallic pipe; and (**b**) metallic pipe. Figure 12: Peak temperature as a function of penetrant area: (**a**) nonmetallic pipe; and (**b**) metallic pipe. Thus, the fire-resistance performance of nonmetallic pipes is highly dependent on opening size, with effectiveness determined by how well the firestop material seals the entire opening. The size or cross-sectional area of the penetrant has a minimal effect on performance when the pipe loses its structure, consistent with earlier findings in Section 3.3 that firestop coverage and distribution ratio are key performance variables.