However, NIST’s WTC 7 investigation did follow the core tenet of NFPA 921, which is the application of the scientific method. The investigation was carefully planned, sources of information were identified and contacted, the building fire and collapse event and the investigation were documented, available evidence was obtained (including documents about the design and construction of the structure), and the origin of the fire was determined based on images, laboratory testing (conducted for the towers, but applicable to WTC 7), and mathematical analyses.
Additionally, in its study of WTC 7, NIST considered all available data and evaluated a range of possible collapse mechanisms: uncontrolled fires on the tenant floors, fuel oil fires, hypothetical blast events, and fires within the Con Ed substation. NIST developed a working hypothesis, modeled the fires and the building, and then used the models to test the hypothesis against the observed behavior of the building. This approach is fully consistent with the principles of scientific inquiry.