After several failed attempts to explain the collapse of World Trade Center Seven, NIST and FEMA have now joined together to release this latest report. In it we find the definitive analysis of the most critical aspects of the collapse, including the final scientific data based on years of investigation and computer modeling.


The full report has been published and it contains some 180 pages, including 20 pages of charts and models. What is offered here is simply a gloss. It is hoped that by reading it the public will at last be satisfied that the case has been solved and that the investigation may now be closed.


  1. WTC7: the “flashpoint model”:


The key piece of evidence here is the discovery of janitorial service orders and memoranda stored off premises in computers at the companies hired by Silverstein, Inc., to clean the offices. By studying the documents from the week of September 11, 2001, NIST scientists made the shocking discovery that toilet paper dispensers in WTC 7 had been filled beyond capacity the morning in question. Not only that, but interviews with cleaning personal that had been on duty that morning indicate that many excess rolls had been stored in basement supply rooms, broom closets, and even (at times) in the stalls themselves.

Cleaning personnel admit that this was strictly against written policy and building fire codes, since the maximum number of toilet paper rolls allowed in a building is regulated by city, state, and federal legislation. Due to various well-understood and documented fire codes that limit the number of rolls based on either number of building employees or square footage, it is not fully understood by experts how these excess rolls slipped through the inspection lists, inventories, and accounting procedures.

Based on these interviews and other eyewitness accounts, and extrapolating from highly sophisticated computer models, technicians from FEMA have estimated that there may have been as many as 17,201 rolls of highly flammable toilet paper in the building at the time of the first fires. Not only that, but by looking at blueprints and floor plans (figs. 1, 2) you can see that this material was spread throughout the building on every floor and in every sector.


  1. Corridors of influence:


The second piece of evidence was discovered by NIST when they noticed that the plumbing in WTC7 might act as a link between these dangerous caches of highly flammable material. As might be expected, a close study of the plumbing grid (fig. 3) shows that every lavatory was connected to every other by a rather short stretch of pipe. It was theorized that fire in one sector would spread to another via these pipes. A loss of fireproofing material on these pipes would facilitate such a spread, by making it impossible to suppress the fire along any given length of pipe.

Top FEMA engineers pointed out to NIST that their laboratory tests had indicated as early as 1976 that methane trapped within the pipes would also facilitate this spread, since any tiny leaks in the pipes would tend to vent gas into the immediate area. Since the pipes were contained within walls, this gas could not disperse in a natural way, and might tend to travel—like the pipe—along certain hidden corridors. This would dramatically augment the already considerable danger, leading, in most foreseeable cases, to a crisis.

Some will think that methane must be in solution in the pipes, but any casual analysis will show that methane does not dissolve in water. Like other gases, methane forms bubbles within the water, and these bubbles may escape at the first opportunity.

Maintenance documents from the period 1980-2000 indicate that the asbestos fireproofing on the pipes had never been removed, although federal law required the removal of all asbestos from buildings during that period. Larry Silverstein indicated to FEMA that he had hired a firm to remove the asbestos, and that they were scheduled to do so in November of 2001. But at the time of the collapse, no work had begun on that.

Previous to the asbestos legislation, it would have been necessary to re-fireproof the plumbing every 25 years. The reason for this is that the asbestos was attached to the pipes with adhesives that had a limited lifespan. Industrial adhesives in the 1970’s and 1980’s had not reached the level of sophistication we now expect, and top scientists in the department of molecular physics at MIT have admitted on record that anywhere from 75% to 99% of the asbestos had probably flaked off by September 2001. At this level of loss, the pipes would have been highly vulnerable to the crisis mentioned above. In fact, the crisis may have reached a critical level do to this very loss of adhesive. As the adhesive degraded and lost its original molecular structure—allowing the asbestos to become detached—it would also allow for the detachment of the adhesive from the pipe itself. This would liberate any underlying weaknesses in the pipe, of whatever nature or size. Leaks that had developed over the years, especially at the joints, would have been automatically sealed by the adhesive. But without this adhesive, the methane would be free to escape in trace quantities, facilitating the quick progression of fire along the length of the pipe.

  1. Simultaneous failure:


Since the building’s 178 lavatories were distributed evenly throughout the entire structure, it can be shown that fire that spread first to these rooms would tend to threaten the building as a whole, and to do so in a balanced manner. A fire in one lavatory could spread via this mechanism to all other lavatories, and it could do so in a matter of minutes. Once the fire reached these rooms, the unreasonable supply of toilet tissue would act as kindling, moving the fire from floor to ceiling and compromising the structural integrity of the sector in question.

Further study of blueprints and floor plans in light of this theory has convinced scientists at NIST that fire seen in windows on the day of the collapse were fires contained in those few lavatories that featured external windows. As you can see (fig. 4), a majority of lavatories in WTC7 were internal rooms; they had no windows. Only 11 of the 178 lavatories featured windows that were visible on the street, and these windows were of course frosted.

Although most of the detritus of WTC7 was shipped to China within months of collapse, NIST was able to gain access to several shards of glass from the building. In the presence of highly interested Secret Service agents and FBI officials, these scientists showed that the frosted shards had been exposed to fire where the unfrosted shards had not. This showed beyond any question that the fires seen from the street were in the building’s lavatories.

Extrapolating from this pivotal evidence, FEMA demonstrated that statistical models showed that the odds of visible lavatories being on fire and non-visible lavatories not being on fire was less than 1 in 430,000. From this we may assume without fear of contradiction that all lavatories in WTC7 were burning quite hot that day.

  1. Private Sector Corroboration:


Following upon this success, the FBI delivered subpoenas to Proctor and Gamble and the International Paper Company to produce internal documents. Upon the receipt of these documents, it was discovered that toilet tissue burns in a controlled fire at approximately 451o Fahrenheit. Independent tests at CalTech, NASA, and the Jet Propulsion Lab confirmed this number to within 3 degrees.1 Some brands such as Charmin’ and Snuggles burned at much higher temperatures, due to the high content of softeners, but no amount of investigation was able to uncover the brand in use at WTC7. As many women worked in the building on a daily basis, there is a statistically high probability that the tissue in question was “squeezably soft” to one level or another. Regardless of the softness of the tissue, with methane as an accelerator this temperature may have reached levels capable of significantly weakening structural steel. There is unanimous agreement to that across all federal agencies.


  1. Timing of collapse:


We have shown the mechanism for initiation of collapse, and the cause of balance, but the speed of collapse also has required explanation. The first two reports were not able to account for this speed, since they had not yet been made privy to the janitorial documents. Now that we have those documents, and the formidable theory that those documents allow, we can prove beyond any doubt that the building collapsed in the only way it could: that is, straight down and very fast.

No one had expected or argued that such a short and squat building would topple over. WTC7 was not a tall skinny building like WTC1 or WTC2, so no one was surprised that it collapsed straight down. But some could not see why all parts would fall at the same time. It was thought that some parts might remain standing, or that some would fall a few seconds later than others. Since we have pointed to the lavatories as the primary initiators of collapse, and since these lavatories were evenly spread throughout the building, it is not difficult to see that the question of simultaneity is answered. But what of the speed? Can we imagine that the lower floors would not inhibit the collapse? Can we imagine that the steel support columns in the interior would all give way simultaneously and completely? Can we imagine that the whole building would fall at the rate of a controlled demolition, just as if explosives had brought it down?

We can indeed, since you can see that explosives of a sort did bring the building down. Not explosives consciously planted beforehand. Not manufactured explosives, not dynamite or any other sort. No, what we had at WTC7 was an explosive thousands of times more dangerous than dynamite: softened toilet tissue and methane gas. No demolition expert could create such a deadly cocktail.

This also explains Larry Silverstein’s oft-quoted comment about “pulling it.” Given the facts we now know, it is clear that Mr. Silverstein was referring to the plumbing. Firefighters in the basement, cued to the problem by maintenance workers, had discovered a huge clog in the sewer main. One of these firefighters informed Mr. Silverstein that the removal of the clog would provide free movement in the pipes above, which would of course allow for the movement of the methane gas within them. It was feared that this methane gas would provide the match to an explosion (the firefighters heroically predicted this even without knowing of the toilet tissue excess). Not realizing the enormity of his action, and preferring a sanitary building, Mr. Silverstein ordered them to “pull it”—an order he now bitterly regrets.




All of this evidence, taken as a whole, can lead to only one conclusion: WTC7 was a ticking time-bomb. A convergence of high-risk presets, combined with gross janitorial and accounting negligence, led to a crisis situation that could not correct itself. Given the dangers inherent in the system, scientists at NIST and FEMA concluded that the tenants of WTC7 were lucky indeed to have escaped without further loss of life. Mr. Silverstein’s order to pull it was rash and unadvised, but this report can show no negligence involved. Under normal circumstances, one would not expect the unclogging of a sewer main to bring down an entire building, and Mr. Silverstein had no foreknowledge of the issue of toilet paper, much less the more technical issues of softeners, adhesives, loss of asbestos, and methane accelerators due to leaks in pipes.


1NASA at first delivered the number 233o Fahrenheit, but it was soon discovered that they had confused Metric numbers with Imperial, bringing the figure back in line with other agencies.