A limited federal metallurgical examination documented severe high-temperature sulfidation with intergranular eutectic melting on two recovered steel members, and its authors stated that no clear explanation for the source of the sulfur had been identified and recommended a follow-up study that has never been performed.

The observation, the explicit absence of an identified sulfur source and the unperformed follow-up recommendation are verbatim in the appendix (SEP-E010). Diagnosticity is limited because the candidate explanations were never tested.

The FEMA appendix explicitly notes severe high-temperature corrosion and intergranular melting, stating no clear explanation was identified. The authors recommended follow-up studies to determine the sulfur source, which were never conducted. The strongest counter-consideration is that this sulfidation may have occurred during long-term heating in the debris pile.

The 2002 FEMA Building Performance Study explicitly documented this high-temperature sulfidation with intergranular eutectic melting on two recovered steel members and noted that the source of the sulfur was unidentified. The authors recommended a detailed follow-up study, which was never carried out. The strongest opposing consideration is that the members were opportunistically recovered with hedged identifications, and the corrosion may simply be the result of long-term heating in the debris pile post-collapse.

FEMA 403 Appendix C documents severe high‑temperature sulfidation and eutectic melting on two steel samples, explicitly states that no clear sulfur source was identified, and recommends detailed follow‑up work that has never been conducted. The strongest objection is that the samples are few, only opportunistically recovered, and the appendix itself notes the corrosion may have arisen from long‑term post‑collapse heating in the debris pile; still, the anomaly and the unperformed recommended study are clearly established.

FEMA’s Appendix C directly observes severe high‑temperature sulfidation with intergranular eutectic melting on two steel samples and explicitly states that the sulfur source is unknown and that a follow‑up study is needed; there is no record this study was ever performed. The main caveat is that the samples’ provenance and whether corrosion was pre‑ or post‑collapse are uncertain, but those points qualify the anomaly’s implications, not its existence or the lack of follow‑up work.

FEMA 403 Appendix C records severe high-temperature corrosion including oxidation and sulfidation with intergranular melting and a liquid iron-oxygen-sulfur eutectic on two recovered members, states that "no clear explanation for the source of the sulfur has been identified," and calls for a detailed follow-up study that the evidence ledger shows has never been performed. The appendix proposes no sulfur source; attributions of a gypsum explanation to these authors are not in this document. The strongest opposing consideration is that the examination covered two opportunistically recovered members with hedged identifications, and the appendix itself raises long-term heating in the debris pile after collapse as a leading possibility, which would carry no implication for the collapse mechanism.

FEMA 403 Appendix C documents severe high-temperature sulfidation with intergranular eutectic melting on two recovered members, states that "no clear explanation for the source of the sulfur has been identified," and recommends a detailed follow-up study that the file shows has never been performed. The appendix proposes no sulfur source; gypsum attributions in circulation belong to a different agency document. The strongest opposing consideration is that the two members were opportunistically recovered with hedged identifications, and the appendix itself raises long-term post-collapse heating in the debris pile as a leading possibility, which would carry no implication for collapse initiation.

The severe sulfidation with intergranular eutectic melting, the explicit statement that no clear sulfur source was identified, and the recommendation for further study are all verbatim in the FEMA appendix. The recommended study has never been performed. The strongest opposing consideration is that the examination covered two opportunistically recovered members with hedged identifications, and the appendix itself raises post-collapse debris-pile heating as a possibility.

The appendix's text is verbatim in the ledger: severe high-temperature sulfidation with intergranular eutectic melting on two members, "no clear explanation for the source of the sulfur," and an explicit recommendation for a detailed study that no institution has performed in the twenty-four years since. The strongest opposing consideration is that the two members were opportunistically recovered with hedged identifications, and the appendix's own leading alternative is post-collapse heating in the debris pile — but that qualifies the anomaly's significance, not the documented facts the claim asserts.

Every substantive element — the severe sulfidation with intergranular eutectic melting, the explicit statement that "no clear explanation for the source of the sulfur has been identified," and the call for a detailed follow-up study — is quoted verbatim from the FEMA appendix, and the case has correctly excised the widespread misattribution of a gypsum explanation to these authors. Confidence is moderate rather than high only because the final clause is a negative literature claim ("never been performed") resting on the absence of any contrary record in this ledger. The strongest opposing consideration is deflationary rather than contradictory: the appendix itself raises post-collapse heating in the debris pile as a possibility, and the two members were recovered opportunistically with hedged identifications, so the anomaly is documented but not localised in time.

Every element of the claim is verbatim in the FEMA appendix: the sulfidation with intergranular eutectic melting, the explicit statement that no source for the sulfur was identified, and the recommendation for a detailed follow-up study (SEP-E010). That no such study exists is supported by its absence from the ledger and by the research agenda. The strongest opposing consideration is that the two members were opportunistically recovered with hedged identifications, and the appendix's own leading possibility is post-collapse heating in the debris pile — but that bears on what the anomaly means, not on whether it was documented and left open.

The observation, the explicit absence of an identified sulfur source, and the unperformed recommendation are verbatim in the appendix. Diagnosticity is limited because the candidate explanations were never tested.