Thought you might enjoy reading the attached article, 

Regards, Frank 

* * *

Okay, Frank, you get another award: The Procrustes Award for stretching the facts to fit the theory.

Meanwhile, since you're interested in pyrotechnics, check out:

http://waronwar.us

Cheers

Kevin 

The Collapse of WTC 1 and 2: A New Theory

F. R. Greening

 “Let us never tolerate outrageous conspiracy theories concerning the attacks of September the 11^th.”

George W. Bush                                                      

1.0Introduction 

At the time of writing, (March 2007), there are three main theories that claim to explain the collapse of WTC 1 & 2: 

1.    The “official theory”: The collapse events were natural, gravitationally driven, processes that were brought on by the localized damage caused by the aircraft impacts and subsequent fires. 

2.    Dr. Steven Jones’ theory: The collapse events were man-made processes caused by the timed ignition of pre-planted explosives or incendiary devices. 

3.    Dr. Judy Wood’s theory: The collapse events were man-made processes induced by an external source of directed energy.  

Needless to say, each of these theories has its supporters and its detractors. Indeed, so much has been written on the pros and cons of each of these theories that there is little to be gained in going over all the arguments one more time. Instead, I recommend to anyone who is not familiar with these theories to simply go to well-known 9/11 websites such as 911Myths, Debunking911 for arguments supporting theory No. 1; Scholars for Truth (Steven Jones’ site) for support for theory No. 2 and Judy Wood and/or Jim Fetzer’s websites for support for theory No. 3.  

However, if any WTC collapse theory is to gain full acceptance it must, at the very minimum, be able to explain certain well-documented phenomena such as: 

· Sudden on-set of the collapse of each tower

· Near free fall descent of the block of floors above each impact zone

· Pulverization and ejection of concrete during the collapse

· The completeness of the destruction of each tower

· Sustained high temperatures in the rubble pile long after 9/11 

Most, if not all, of these phenomena have been quoted as being problematic in some way to the currently proposed collapse theories. In this article a new theory of the WTC collapse is presented – one that involves the use of pre-planted ammonium perchlorate (AP) based mixtures – that is able to explain these and other important characteristics of the demise of WTC 1 & 2. In many respects, the new theory, which I will refer to as the AP theory (or theory No. 4, if you prefer!), is similar to Steven Jones’ pre-planted thermite/explosives theory. However, as this report will show, the use of AP as an incendiary/explosive is preferable to thermite mainly because it avoids the problems associated with complex wiring and detonator devices that would have been required to ignite thermite-based incendiaries or conventional explosives.  

2.0The Ammonium Perchlorate-Assisted-Collapse Theory 

Background: 

Ammonium perchlorate, NH₄ClO₄, is a colorless, odorless, compound that is stable at room temperature. However, when heated to above 300 °C, or subjected to friction or impact, it becomes violently reactive. In fact, ammonium perchlorate is a much-used ingredient in explosives, pyrothechnics and solid propellants such as those used in the space shuttle booster rockets. 

The decomposition reactions of ammonium perchlorate are complex and variable: Cl₂, HCl, NH₃, N₂O, NO, N₂, H₂O and O₂ have been consistently observed as major products. The decomposition reaction is highly exothermic, releasing about 2 MJ/kg of heat energy, and is accompanied by the production of about 800 liters/kg of gases. The combustion of ammonium perchlorate in oxygen-rich atmospheres produces a diffusion flame at about 3200 °C  

The decomposition of samples of pure ammonium perchlorate at 225 °C is 25 % complete after 4 hours. However, if the ammonium perchlorate is mixed with suitable metal oxide catalysts the decomposition is accelerated. Among the large number of metal oxides that have been investigated as AP decomposition catalysts, such as Al₂O₃, CaO, Fe₂O₃ and MnO₂, manganese dioxide is found to be by far the most effective. Thus an addition of 10 % by weight of MnO₂ to ammonium perchlorate increases the decomposition rate by a factor of about 2. Based on these properties of ammonium perchlorate / manganese dioxide mixtures, the following scenario is presented as a new collapse theory: 

1. The Twin Towers were Primed with AP: 

Ammonium perchlorate powder, probably containing up to 10 wt % manganese dioxide and other additives (e.g. Al, HMX, etc.), was prepared and mixed with one or more of the five spray-on fire resistive (thermal insulation) materials used in WTC 1 & 2. These materials are identified in NIST NCSTAR 1-6A as: (1) Blaze-shield Type D, (2) Blaze-shield Type DC/F, (3) Blaze-shield Type II, (4) Monokote MK-5, and (5) Vermiculite aggregate plaster. In order to determine where and when these material were applied to surfaces in the Twin Towers we need to consider the history of the “passive fire protection” practices employed by the New York Port Authority during and after the construction of the towers, starting in 1970 and ending in 2001.  

On April 13, 1970, New York City issued a ban on the use of all sprayed on thermal insulations containing asbestos, the notorious fibrous silicate mineral that was a major component of Blaze-shield Type D. The use of asbestos-containing insulation was discontinued at this time at the 38^th floor of WTC 1. In February 1975, a fire occurred in WTC 1 that affected floors 9 to 19 and led to a review of the adequacy of the existing thermal insulation in the entire WTC. The need to upgrade the passive fire protection in the Twin Towers was finally addressed in 1995 when, after yet another study, it was decided to apply a 1½ inch thickness of an asbestos-free spray-on mineral fiber fire protection material to selected steel surfaces. Thus, between 1995 and 2001, thermal protection was upgraded specifically on 18 floors in WTC 1, including floors 92 to 100 and 102; and on 13 floors in WTC 2 including floors 77, 78, 88, 89, 92 and 97. (See NIST NCSTAR 1-6A page xxxvii).  

How much thermal protection was used? A reasonable estimate would be a thickness of 2 cm over an effective area of 2500 m² or 50 m³ per floor. If we assume the material had a density of 400 kg/m³ there would have been 20 tonnes of thermal protection per floor.  

It should be noted that the specific floor selection would have made on the basis of the need to apply fire protection material to a particular area. Thus protection would have been sprayed on areas that were known to be vulnerable to fire damage. However, in the AP theory, the fire protector was, in fact, a fire accelerant or pyrotechnic, most probably an ammonium perchlorate/manganese dioxide mixture blended with a portland cement-based binder, or something similar. Given the fact that upgrading of the passive fire protection of WTC 1 & 2 was an on-going project throughout the late 1990s, a deadly pyrotechnic coating could have been applied almost anywhere and at any time during this period. If we assume that the normal cement-based material was “spiked” with 25 wt.% of our pyrotechnic mixture, up to 5 tonnes of ammonium perchlorate could have been sprayed onto a designated floor. Furthermore, once applied to a particular floor, the coating would have remained undisturbed, unnoticed, and with no loss of potency, until it was triggered by the events of September 11^th 2001.  

2. Boeing 767 Aircraft Strike the Towers and Start Fires 

It is documented in the NIST and FEMA WTC Reports that the aircraft strikes on the Twin Towers on the morning of September 11^th 2001 inflicted major structural damage to several floors of each tower. NIST’s assessment of the damage is based on modeling of a Boeing 767 aircraft, weighing about 125 tonnes and traveling at about 500 mph, crashing into each tower and igniting about 30 tons of jet fuel. A spectacular fireball was seen after each aircraft impact and the blast overpressure caused considerable damage to office furniture, wallboards, ceiling tiles and windows on the impacted floors. However, it is believed that this over-pressure was insufficient to have damaged the structural steel support columns; hence, structural damage that did occur was inflicted by direct kinetic energy transfer.  

On the other hand, if ammonium perchlorate-impregnated insulation was pre-planted on the upper floors of the Twin Towers and was subsequently subjected to hard impact, a violent detonation would have occurred which would have greatly intensified the energy release compared to a simple fuel-air deflagration. What is more important, however, is that the protracted fires that followed the aircraft impacts would have been more damaging than expected if the upper floors of the towers were primed with ammonium perchlorate - a potent oxidizing agent that would have been activated as the surface temperatures in affected areas reached 250-300 °C.  

NIST carried out fire resistance testing of simulated WTC floor (truss) assemblies, (See NIST NCSTAR 1-6A and 1-6B), using procedures prescribed by ASTM E-119: “Standard Methods for Fire Tests of Building Construction and Materials.” One of the most significant findings was that test specimens protected with ¾ in. thick fire-resistive material reached 300 °C in about 45 minutes at which point the top chords yielded due to the difference in thermal expansion of steel and lightweight concrete. However, other tests and/or computer simulations indicated that the steel temperatures of WTC 1 & 2 floors and exterior columns were generally lower than 300 °C.  

It is concluded by NIST that although insulated floors thermally expanded and pushed outwards on the exterior columns, thereby sagging up to 8 in., the floor sag was insufficient to pull-in the exterior columns. In view of this finding, NIST have proposed that thermal insulation must have been displaced by the entry of the Boeing aircraft into the impact zones of each tower, namely, floors 94 to 98 in WTC 1 and floors 78 to 83 in WTC 2. This loss of thermal insulation allowed floor and column assemblies to reach temperatures in excess of 600 °C. It is also estimated by NIST that exterior column pull-in was significant above 560 °C at which point the truss seat bolts sheared off.      

Let us now reconsider the NIST description of the collapse of WTC 1 & 2 in the light of the suggestion that the passive fire protection coating was spiked with 25 % of an ammonium perclorate – manganese dioxide (AP) mixture. It is proposed that three decomposition behaviors would result depending on the local temperature and rate of heating: 

(i)           For slow heating up to 250 °C: a gradual exothermic decomposition of the AP would occur.

(ii)         For rapid heating in the range 250 – 350 °C: a fast exothermic decomposition of the AP would occur.

(iii)       For rapid heating to temperatures above 350 °C, or under impact loading: detonation of the AP would occur.  

The fire-resistant coatings in the Twin Towers were located in covered and relatively inaccessible areas. Consequently, AP decomposition modes (i) and (ii) would not have been visible from outside the towers. Nevertheless their effects would have been highly detrimental to the integrity of floor trusses and adjacent areas as the following calculation demonstrates: 

Mass of steel trough decking per floor = 16 tonnes 

Mass of ammonium perchlorate coating per floor (See item 1 above) = 5 tonnes 

Heat of decomposition of ammonium perchlorate = 2 MJ/kg  

Heat released by the complete decomposition of 5 tonnes of AP = 10,000 MJ 

Heat capacity of iron = 0.45 kJ/kg 

Heat required to raise the temperature of 16 tonnes of steel by 1 °C = 16,000 ´ 0.45 kJ =  7.2 MJ 

Hence, the maximum temperature increase produced by reaction of 5 tonnes of AP =  1390 °C 

This would have been enough heat to melt the steel decking! However, on a cautionary note, the above calculation is very approximate because it ignores questions of heat transfer to the steel. Nevertheless, as a first approximation, it clearly illustrates the potential for major heat damage to the flooring system by an AP-spiked coating. This degree of heat generation also provides a mechanism for the formation of the much-debated “molten steel” at the WTC.  

3. The Twin Towers Collapse in a Shower of Dust and Debris 

The record shows that on the morning of September 11^th, 2001, WTC 1 was impacted by a Boeing 767 aircraft at 8:46 a.m. and collapsed 102 minutes later at 10:28 a.m. WTC 2 was similarly impacted at 9:03 a.m. and collapsed 56 minutes later at 9:59 a.m. The NIST collapse initiation theory for the Twin Towers involves a gradual weakening and overloading of structural steel members in the impact damaged, fire-affected zones of the buildings. However, it is very important to note that the loss of portions of the passive thermal protection in the fire-affected zones of WTC 1 & 2 is crucial to the viability of NIST’s theory.  

In our new WTC collapse theory the NIST model is still, in a sense, valid but the need to invoke the loss of passive thermal protection is obviated by the proposed spiking of the fire retardant with the potent oxidizing agent ammonium perchlorate. Thus, far from protecting the buildings from fire damage, the sprayed-on coating, once activated, would have actually heated the floor assemblies so severely that catastrophic failures in susceptible areas such as the truss seats eventually occurred. The details of this process are controversial, but whatever precipitated the final collapse of the Twin Towers, the results were rapid and decisive. And it was during the ensuing 12 - 15 second collapse intervals that the deadly ammonium perchlorate coating first revealed its presence to the world in a very dramatic way.    

The near free fall descent of the upper sections of WTC 1 & 2 has been much discussed; so too has the in situ pulverization of the concrete. While these phenomena are potentially explicable within a gravity driven collapse scenario, the overall behavior of the ejected dust and debris was quite remarkable but is well accounted for by our new collapse theory. First, it should be recognized that the ammonium perchlorate that is postulated to have been applied to the upper sections of WTC 1 & 2 would have been activated by the jet fuel fires prior to collapse initiation and, as the AP decomposed, it would have made the affected surface coatings very hot and friable. In addition, gas generation associated with the decomposition reaction (800 liters per kg) would have made the coatings exfoliate so that falling sections of coated material would have left pronounced trails of dust. Furthermore, since AP detonates under moderate impact loading, coated building sections falling onto the floors below would have set off explosions resulting in violent ejections of pulverized material, as was observed during the collapse of WTC 1 & 2. 

We have previously proposed that up to 5 tonnes of ammonium perchlorate was applied to selected upper level floors in WTC 1 & 2 and now suggest that ~ 15 floors were treated with this chemical so that the total loading of ammonium perchlorate was about 75 tonnes per tower. If 50 % of the available AP reacted before or during the collapse of each tower, ~ 30 million liters of hot and potentially corrosive gases such as HCl, Cl₂ and NO would have been released by the time the rubble pile was formed. In any case, the remaining 50 % of the AP would eventually also react in the smoldering rubble pile, as we shall now discuss.  

4.    The Rubble Pile Stays Hot and Cooking for Months after 9/11 

The massive rubble pile that formed at Ground Zero as a result of the collapse of WTC 1 & 2 was notable in many ways but in the present context we need to focus on only two features of the pile: its sustained high temperatures and its toxic emissions. Elevated temperatures (over 600 °C – see below) were observed at many locations within the rubble pile and remained high for several months after 9/11. These sustained high temperatures are indicative of exothermic chemical reactions within the pile that need to be explained. Similarly, while toxic emissions from a burning building are to be expected, the chemical make-up of the emissions measured at, or near, Ground Zero was highly unusual. Nevertheless, as we shall discuss below, residual ammonium perchlorate at Ground Zero offers a convenient explanation of both the sustained high temperatures, and the gaseous emissions from the rubble pile. 

The Sustained High Temperatures:

In an article in the October 2003 issue of Chemical & Engineering News, L. Dalton has summarized the progress of the fires and the associated temperatures within the WTC rubble pile:

“The fires, which began at over 1,000 °C, gradually cooled, at least on the surface, during September and October 2001. USGS's AVIRIS  measured  ground temperatures when it flew over the WTC site on Sept. 16 and 23. On Sept. 16, it picked up more than three-dozen hot spots of varying size and temperature, roughly between 500 and 700 °C. By Sept. 23, only two or three of the hot spots remained, and those were sharply reduced in intensity, researcher Clark said.However, Clark doesn't know how deep into the pile AVIRIS could see. The infrared data certainly revealed surface temperatures, yet the smoldering piles below the surface may have remained at much higher temperatures. "In mid-October," said Thomas A. Cahill a retired professor of physics and atmospheric science at the University of California, Davis, "when they would pull out a steel beam, the lower part would be glowing dull red, which indicates a temperature on the order of 500 to 600 °C. And we know that people were turning over pieces of concrete in December that would flash into fire--which requires about 300 °C. So the surface of the pile cooled rather rapidly, but the bulk of the pile stayed hot all the way to December."

NIST estimates that the heat release rate of the fires in WTC 1 & 2 in the time period just before the collapse of these buildings was about 0.5 gigawatts. We will assume that burning material and fresh combustible live load material was transferred en masse to a depth several meters below the top of the rubble pile where it continued to burn. Initially the heat flux near the top of the rubble pile would have been as high as 100 kW/m² with an inferred combustion rate of about 25 kg/s. However, as the initial oxygen supply from air pockets within the rubble pile dwindled, the combustion rate and heat flux would have declined until it was reduced to a smoldering state.

Smoldering is a well-studied and quite reproducible phenomenon. It is observed in man-made situations such as garbage dump or tire-pile fires, and in the natural environment in forest fires. Smoldering is usually quantified in terms of the velocity at which the char front advances, as in the well-known example of a cigarette. In stationary air, the smoldering of compressed cellulose-based material proceeds at very consistent rates in the range 10^-3 cm/s. Thus we see that, in the period immediately after 9-11, a zone existed several meters below the top of the rubble pile where combustible material burned in a self-sustaining, smoldering condition. Furthermore, in the presence of an adequate supply of oxygen, this smoldering combustion could have continued until the supply of “fuel”- office furniture, paper, textiles and plastic materials - was exhausted. However it is important to note that this smoldering mass could only have sustained temperatures up to about 350° C and we know the rubble pile was hotter than this!

This picture changes dramatically if we assume that un-reacted ammonium percholrate was present in the rubble pile. In item 3 above, we have already suggested that up to 50 % of the initial loading of AP could have found its way into the rubble pile; for two towers this would have been about 75 tonnes of un-reacted AP. Now, because the thermal decomposition of ammonium perchlorate releases about 2 MJ/kg of heat energy, a total of 150 GJ would have been available from this source. Furthermore, because the smoldering material in the rubble pile was already capable of generating and sustaining temperatures of 350 °C, the conditions in the pile would have been quite sufficient to initiate the AP decomposition reaction in localized areas. What is also very significant is that water, (which was in great supply during recovery operations at Ground Zero), is known to “rejuvenate” partly decomposed AP, (See Proc. Roy. Soc. A227, 115, (1954)) 

It is, of course, quite difficult to estimate the temperature that a rubble pile “spiked” with AP could attain but we note that temperatures in excess of 600 °C have been recorded at the surface of “burning” AP (See Chemical Reviews Vol. 69, 551, (1969)). However, this is just the beginning of the heating effects of pre-planted AP in the Twin Towers because we need to also consider the fate of the gaseous decomposition products of AP, especially the reactive species oxygen, chlorine, hydrochloric acid, nitric oxide and ammonia. Alone, or in the presence of water vapor, these gases would be extremely reactive towards metals such as iron and aluminum that were present in the rubble pile. For example, the reactions of iron with the O₂, HCl and Cl₂ released from the thermal decomposition of 1 kg of ammonium perchlorate would release about 3 MJ of heat energy. 

Gaseous Emissions from the Rubble Pile

To establish supporting evidence for an ammonium perchlorate theory it is helpful to look for “chemical signatures” of the presence of ammonium perchlorate in the rubble pile. This requires careful scrutiny of the available data on gaseous emissions at Ground Zero. For example, consider the Report on Air Sampling Near the World Trade Center Site: New York State Department of Health, October 30 & 31, 2001.” In this document we find that air sampling of the smoke plume on the rubble pile over one month after 9/11 measured 33.9 mg/m³ of HCl as well as 2.24 mg/m³ of HNO₂ and 12.28 mg/m³ of HNO₃. The presence of these acid gases in the air above the WTC rubble pile at this time is consistent with the emission of Cl₂, HCl, N₂O, NO, and H₂O from the slow decomposition of ammonium perchlorate.

Prof. T. A. Cahill at U.C. Davis has also published data on aerosol samples collected at or near Ground Zero in October 2001. (See Aerosol Science and Technology 38, 165, (2004)) Among the data reported by Cahill is a mass spectrum of 5 – 2.5 mm particulate collected from within the smoke plume on Varick Street. In agreement with the results noted above, the mass spectrum’s three strongest peaks reveal the presence of Cl, NO₂ and NO₃. However, Cahill suggests that the detection of chlorine may be explained by “ the relatively large chlorine inventory in the WTC buildings from plastics, including the ubiquitous PVC, and chlorine-bleached paper.” Let us therefore briefly review data on chlorinated species at the WTC in relation to studies of the behavior of chlorine-containing materials such as PVC in building and other related fires.

Analytical data reported by the US EPA derived from air monitoring at, or near, Ground Zero in the period September 2001 to May 2002 show that many chlorinated organic species were present at significant levels up to December 2001. These included aliphatic species such as chloroform, chloroethane and di-chloroethane as well as the aromatic compounds chlorobenzene and di-chlorobenzene. The maximum concentrations observed for these and related species are given in Table 1. The compounds listed in Table 1 are arranged into two groups: chlorinated species produced by the thermal degradation of PVC and chlorinated species that are not derived from PVC decomposition. The PVC-derived designation was arrived at from published data on the thermal decomposition of PVC, (See for example: Journal of Polymer Science 12, 737, (1974)). Apart from HCl, which is indeed a major product of the thermal degradation of PVC, the major decomposition products from heating PVC in the temperature range 300 – 500 °C are: benzene, toluene, ethylbenzene, chlorobenzene, di-chlorobenzene and tri-chlorobenzene. As Table 1 shows, all of these species were observed in the air at Ground Zero. Furthermore, the relative abundances of the PVC-derived compounds in Table 1 are consistent with literature data on the thermal decomposition of PVC. 

Table 1.      Major Chlorinated and Related Organic Species Observed in the Air at Ground Zero (EPA Data: September to December 2001)

Source Type	Compound	Maximum Concentration  (ppb)
PVC Degradation Product	Benzene	180,000
	Toluene	74,000
	Ethyl Benzene	67,000
	Chlorobenzene	1,900
	Di-chlorobenzene	1,540
	Tri-chlorobenzene	57
Non-PVC Origin	Chloroform	2,000
	Chloroethane	3,200
	1,2 di-chloroethane	2,100
	Tri-chloroethane	1,300
	Tetra-chloroethane	140

However, the most interesting feature of the data in Table 1 is the fact that the non-PVC-derived chlorinated species are more abundant than the PVC-derived species. This clearly demonstrates the presence of another major source of chlorine, above and beyond “the ubiquitous PVC” previously postulated by Prof. Cahill as the most likely source of the elevated levels of chlorine in air samples collected at Ground Zero up to December 2001.

An alternative source of chlorine suggested by Prof. Cahill, namely chlorine-bleached paper, may also be ruled out as a major contributor to chlorine emissions at Ground Zero. Thus, while there certainly was certainly a large amount of paper in the Twin Towers, a reasonable upper limit would be 500 kg per office ´ 100 offices per floor, or 50 tonnes of paper per floor. However, paper typically contains no more than 0.5 wt. % of chlorine so that each floor would have contributed a maximum of only 250 kg of chlorine to the total inventory of chlorine in the Twin Towers. This should be compared to a chlorine contribution of about 1500 kg per floor if ammonium perchlorate was pre-planted to the concentrations we have previously suggested.

In conclusion we note that a full consideration of all the potential sources of fluorine and chlorine in the WTC shows that CFC refrigerants such as Freon-22, (chlorodifluoromethane, CHClF₂), used in the central air conditioning system, as well as the floor-specific fire suppression agent Halon 1301, (bromotrifluoromethane, CBrF₃), were significant additional sources of Cl and F. 

3.0Summary and Conclusions (with Physicochemical Evidence for Molten Iron)

The effect of adding the pyrotechnic agent ammonium perchlorate, NH₄ClO₄ (AP), to the thermal insulation/fire-protective coating used on the upper floors of WTC 1 & 2 has been considered. It is noted that exothermic decomposition of an AP “spiked” coating, initiated at ~ 300 °C, would have had catastrophic consequences to the integrity of the buildings at or above the impact zones in each tower. The most detrimental consequences of the presence of kilogram quantities of the energy-rich oxidizing agent ammonium perchlorate would have been in fire-ravaged areas of WTC 1 & 2 where rapid “shock-heating” of floor assemblies would have lead to:

(i)           Differential thermal expansion causing buckling or fracture of floor elements

(ii)         Complete collapse of entire floor sections

(iii)       Explosive spalling and “powderizing” of the concrete.

(iv)        Melting of the corrugated steel floor pans

With the possible exception of item (iv), these four phenomena are well-known features of the collapse of WTC 1 & 2. But let’s consider the evidence for item (iv) and the crucial question of molten steel in the WTC rubble pile at Ground Zero in more detail. While this topic has been debated on many 9/11 websites, nearly all of the arguments I have seen rely on visual sightings of “molten metal” in the rubble pile - information drawn from eyewitness accounts recalled by recovery workers. This type of anecdotal evidence has been strongly criticized for its lack of scientific credibility. Remarkably, however, there is some crucial scientific evidence for the presence of molten iron or steel in the pulverized remains of WTC 1 & 2 that has apparently been completely ignored by 9/11 researchers.

I am referring to the observation of micron-sized iron spherules that have been seen in many WTC dust samples. These spherical particles are direct physical evidence that the iron within the particle was molten at the time the particle formed.

Each of the references below specifically mention the detection of iron spherules in WTC dust samples (and in most cases also provide electron micrographs of the particles in question). Reference 1 includes two such micrographs labeled IRON-03-IMAGE and IRON-04-IMAGE. Reference 2 discusses which WTC particles could best be used as signatures of WTC dust; iron spheres were considered and rejected only because they were not found in all indoor dust samples. In reference 3 we read on page 17: “Various metals (most notably iron and lead) were melted during the WTC event, producing spherical metallic particles.” And finally in reference 4 we find a micrograph of a spherical iron particle and the comment that WTC dust contains evidence for “heat effected particles, including spherical particles.”

1.    H. A. Lowers et al. “Particle Atlas of World Trade Center Dust.” USGS Open-File Report 2005-1165, (2005) 

2.    Various authors: “U.S. EPA Response to the Peer Review of the U.S. Environmental Protection Agency’s Final Report on the World Trade Center Dust Screening Study.” Page 28, (December 2006)

3.    R. J. Lee et al. “Damage Assessment 130 Liberty Street Property: WTC Dust Signature Report on Composition and Morphology.” Issued December 2003.

4.    S. R. Badger et al. “World Trade Center Particulate Contamination Signature Based on Dust Composition and Morphology.” Microscopy and Microanalysis 10 (Supplement 2), 948, (2004).

 

The formation of spherical iron particles has been well documented and researched for steel making processes, (See for example: Steel Research 64, 23, (1993) and Steel Research 72, 324 (2001)). Iron spheres in the 30 mm to sub-micron range are typically seen in the dust-laden off-gases produced by molten steel and are believed to be formed by the ejection of metal droplets when the liquid metal degasses.     

In seeking an explanation of the formation of iron spherules during the destruction of WTC 1 & 2 it is significant that samples of WTC dust have an additional chemical signature - an enrichment of zinc. Data for iron and zinc in WTC aerosol samples have been presented by S. Qureshi and co-workers in Atmospheric Environment 40, S238, (2006). We first note that concentrations of these elements in PM_2.5 aerosol collected in New York City prior to 9/11 were about 100 ng/m³ for iron and less than 20 ng/m³ for zinc. Qureshi’s data show that on September13 2001 the PM_2.5 iron concentration was 127 ng/m³ and the zinc concentration was  217 ng/m³, i.e. airborne zinc concentrations were about ten times higher than normal. Qureshi’s data also show that both iron and zinc concentrations in New York’s 2.5-micron dust peaked in early October 2001 with iron at 370 ng/m³ and zinc at a remarkable 1028 ng/m³. These observations are consistent with iron and zinc data reported by the EPA for WTC air monitoring samples collected in the same post-9/11 time period.  

Why was so much zinc dispersed into the air above Ground Zero? In order to answer this question we need to consider sources of zinc in the Twin Towers. A review of the construction materials in these buildings shows that the galvanized 22-gauge corrugated sheet steel, used for the decking that supported the floor concrete, was a major source of zinc. Given that 22-gauge galvanized steel has a coating of about 50 mm of zinc on a 1 mm sheet of metal comprised of ~ 98 % iron, we may use our previous estimate of 16 tonnes for the mass of steel decking per floor to conclude that there was about 1.6 tonnes of metallic zinc on every floor in WTC 1 & 2. 

We have shown in the first part of this article that if some of the thermal insulation that was applied to floor assemblies in the Twin Towers was spiked with 25 % by weight of ammonium perchlorate and subsequently exposed to jet-fuel fires, it would have heated the steel decking to ~ 1390 °C. Now, since the boiling point of zinc is 908 °C, this degree of heating of a floor assembly would have been sufficient to vaporize the zinc in the galvanized steel!  

To conclude: we have shown that an AP collapse theory accounts for all four processes that collectively led to the observed level of destruction to WTC 1 & 2, namely: the buckling and fracture of floor elements; the collapse of entire floor sections; explosive spalling and “powderizing” of the concrete; melting of the floor pans. As an aside, we note that the addition of ammonium perchlorate to the thermal insulation on the upper floors of the Twin Towers comes very close to being the perfect crime. The deadly AP-spiked concoction would have been almost identical to the un-spiked coating; it could have been sprayed on selected surfaces with impunity; it required no elaborate detonator devices to be activated – moderate heating worked just fine. And finally, because AP decomposes to gaseous products, it leaves no telltale residues. Of course, I haven’t proved that AP was used in the Twin Towers, but to end with a famous quote:  

“How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth……..”  

The Sign of Four by Arthur Conan Doyle                                                                              

F.R. Greening, March 15^th, 2007