Thermal-Response Heterogeneity and Localized Heating Anomalies in Nominally Identical Fire-Resistant Glazing

The variability of thermal protection provided by nominally identical fire-resistant glazing panes is poorly captured by the pass/fail outcome of full-scale fire-resistance tests. We re-analysed 15-s unexposed-surface temperature histories from 60 same-type, full-size panes nested within seven heterogeneous EI 30 partition tests. Between 30 and 45 min, the median within-test interquartile range increased from 1.59 to 5.20 K; an increase was observed in six of seven tests. A complementary maximum-above-median measure exposed individual heated panes even where the interquartile range did not increase. A five-minute differential descriptor identified two early accelerated responses (T2-G2 and T5-G6) in a common observation window, whereas two additional original flags arose only later during longer exposures. Time to a 140 K mean pane-temperature rise ranged from 8.12 to 33.91 min; this descriptor is not an additional fire-resistance rating. The exploratory lower-tail calculation was sensitive to rare components and cannot establish an independent pane-count effect. These findings demonstrate substantial heterogeneity and distinct anomalous trajectories within one nominal glazing product while preserving the original EI 30 classification.