Review on the Assessment of Safety and Risks, CHEMIA I PIROTECHNIKA, Chemia i Pirotechnika

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296
Propellants,Explosives,Pyrotechnics 26,296–301 (2001)
Review on the Assessment of Safety and Risks
Carl-Otto Leiber*
Fraunhofer-Institut f¨r Chemische Technologie (ICT),D-76327 Pfinztal (Germany)
Ruth M. Doherty
Naval Surface Warfare Center,Indian Head,Maryland (USA)
Dedicated to Dr. Axel Homburg on the Occasion of his 65th Birthday
Summary
be controlled by sensitivity data. From this conclusion it is
inferred that very insensitive explosives should not be prone
to unwanted explosion catastrophes. But explosion hazards
of chemicals that are not considered to be explosives teach us
that this assumption is misleading. Also explosives sensiti-
vity testing shows that current methods cannot predict such
explosion hazards. Therefore,the instruments for safety
show great value,but can fail completely in some cases.
Whereas the explosion of explosives is an experience over
hundreds of years,explosion accidents not based on explo-
sives was experienced very late in the last decades. Never-
theless these had been present in nature allover the lifetime of
the universe.
Never it had been attempted to consider all these explosion
events under a common view. It is challenging,therefore,to
search for possibly joint elements. One only knows,that any
understanding is too poor to allow prediction of these events.
If the dimensions in nature or in the technical world get large,
mostly effective help is not possible if such catastrophes
result.
Historically explosion accidents are linked with energetic materials.
There is the further belief,that the proneness to accidents—and their
severity—is linked with the sensitivity of these explosives. Conse-
quently there exist seemingly very insensitive materials for which it is
believed that their accidental explosion can be ignored,so that safety
distances can be reduced to those that apply to materials for which the
hazard is assumed to be mass fire rather than mass detonation. Evi-
dence is presented here that shows these assumptions to be invalid.
Reports of explosion accidents are gathered here for substances that
are not generally considered to be explosives (non UN-class 1 sub-
stances,like ammonium nitrate (AN),neat alkali metal chlorates,and
even hypochlorites and nitromethane). In most of these cases the
proneness of accidents had not been foreseen by testing.
The basic explosion mechanisms are of a more general nature than
simply those that apply to high explosives. Explosion is not solely a
matter of energy,but of any physical power conversion. In order to
prove this,a survey of explosion events is given: Natural events,like
the impacts of celestial bodies and volcanic eruptions. Fuel=liquid
interactions in nature are industrial risks too,which occur at very
different occasions and sites: Cellulose processing,the oil industry,
foundries,power stations,explosions of hot cinders,chemical pro-
cessing,fire extinguishing,and (most common) in the kitchen,and
(most catastrophic) in nuclear reactors. Explosions of similar type are
Hydraulic Transients,Bubble resonance explosions with the possibility
of associated chemical room explosions (BLEVE),Rollovers. Second
order effects are sorption=desorption resonance explosions,which
most powerful also occur in nature (Nios Lake (CO
2
-release),Kivu
Lake,Monoun Lake,1984,Tanganjika Lake,all in Africa,and the
Ocracoke in the Gulf of Mexico (CH
4
-release)—and at the lowest end
shaken champagne bottles.
All these explosions are ‘‘low probability–high risk’’ explosive
phenomena,which are scarcely coverable by risk studies with the pre-
sent day scientific tools on explosion phenomena. Up to now only in the
nuclear branch a quantitative risk of explosion was brought to attention,
therefore,the validity of this approach was carefully examinated.
2. Early Experiences with Explosives
While explosions have occurred with black powder over
the centuries,the discovery and industrialization of nitrocot-
ton by Sch¨nbein,and nitroglycerine by Sobrero and Nobel
in the second half of the last century was a bloody success
story. Nearly all possible failures leading to catastrophes with
these materials have been experienced. It was learned that
heat,shock,friction,chemical compatibility,phase transi-
tions,all kind of sparks and so on can cause for explosions. At
the time of this development,the influence of viscosity and
the heterogeneity of the explosive on its sensitivity had been
recognized (blasting gelatin) but the general applicability of
these principles was not too widespread.
Nitrocotton powder,poudre B,and picric acid were used in
military applications after their commercial development,
and military use was based on civil practice. Considering the
consumption of military and commercial explosives over 100
1. Introduction
Classical explosions of usual explosives are attributed to
stimuli and threats,which beyond a certain sensitivity level
(can) lead to explosions. Therefore,explosion events seem to
* Corresponding author; e-mail: C.O.Leiber@t-online.de,formerly
member of WIWEB,Swisttal-Heimerzheim.
# WILEY-VCH Verlag GmbH,D-69469 Weinheim,2001
0721-3115/01/0612–0296 $17.50þ:50=0
Propellants,Explosives,Pyrotechnics 26,296–301 (2001)
Review on the Assessment of Safety and Risks 297
years,this was a good deal. It is less widely known that the
amount of commercial explosives consumed exceeds at least
by an order of magnitude that of military explosives (exclud-
ing the time of the world wars). This is also the reason why
there is considerable feedback of experiences regarding the
safety of commercial explosives,which is usually not present
to such an extent for military articles. Therefore,with respect
to explosion phenomena and irregularities,we get the most
input from the commercial side,see Table 1.
detected phenomena that we attribute today to Low Velocity
Detonation phenomena,the officially adopted reason was
that,most probably,the double salt (ammonium nitra-
te=ammonium sulfate) demixed. But a regulation was
issued: Do not blast ammonium nitrate containing mixtures.
Even after the Oppau experience,no instrumentation was
developed that could predict such a hazard. More cata-
strophes of the same (Tessenderloo,Belgium,1942) or
similar kind resulted. Examples are Texas City (1947),
Brest (1947)
(9)
,the Black Sea,and Japan for ammonium
nitrate initiated by external fires. None of these accident
investigations resulted in a means of evaluating the risk
associated with these materials. But we must keep in mind
that the most common response of ammonium nitrate to an
external fire is burning.
Other explosion hazards have been observed around the
world with non UN-class 1 substances. Some of these have
occurred spontaneously (by marshaling—i.e.,handling in
railway yards),but usually they are caused by external fires.
Examples are nitromethane explosions,1958
(13)
,MMAN-
explosions
(14)
(marshaling),and explosions of pure chlo-
rates,perchlorates and even bleaching powders by external
fires. These have been known since 1899. The latter sub-
stances do not show any indication of an explosion hazard by
classical testing. One can speculate,therefore,on what is the
point of such tests,which cannot even predict the cratering
risk if a drum falls from the table to the floor.
The most insensitive explosives and articles are assigned
to UN-class 1.5 and 1.6,defined by appropriate testing
(15)
.It
is stipulated that the probability of any accidental explosion
is negligible. Therefore,reduced safety distances based on
the expectation of mass fire rather than mass detonation,are
thought to be adequate. Serious consideration should be
given to whether such a conclusion is really acceptable. For
the following reasons it really is not. Originally,the UN-class
1.5 had been created for ANFO- and slurry-explosives,which
are used as explosives,but in hazard classification tests show
no apparent explosive properties. Nevertheless,the compar-
ison of explosion hazards shows that there are a greater
number of explosion hazards on 1.5-substances compared to
explosives like TNT and others
(16)
. (In order to remain honest,
we should note that much larger quantities of commercial
explosives are produced than classical 1.1-explosives.)
3. Catastrophic Interaction between Theory and
Safety
Explosion accidents in which the cause can be found in
classical threats occur with military as well as industrial
explosives. But there are also accidents for which the cause is
less obvious,or is not explainable in current terms. For any
assessment of the cause,an insight into explosives behavior,
usually provided by a model or theory,is necessary.
The physical phenomenon of the detonation of gases was
discovered in 1882 by Mallard and Le Chatelier,and also
Berthelot and Vieille. In 1893 Schuster
(12)
made a discussion
note to Dixon’s lecture on gas detonation. This discussion
note just contained in principle the current detonation theory.
It is remarkable,that Schuster also pointed out the weakness
of this theory. But this theory,known as the piston model of
detonation,was so successful for gases that it was also applied
for condensed explosives. A plane piston in motion com-
presses and heats up the material until by thermal means a
decomposition occurs,which drives this piston,and plane
detonation waves result. This was the origin of the thermally
driven detonation.
In accordance with this theory,supported by ‘‘appropriate’’
testing,at the beginning of the last century it became
common practice,approved by authorities,to loosen heaps
of ammonium nitrate (AN) by blasting procedures. After the
first accidents,the ammonium nitrate was desensitized
(Oppau-salt),until the first large industrial catastrophe of
the last century resulted. Even after this catastrophe by
classical testing—also applied nowadays—this risk could
not be evaluated. In spite of the fact that Poppenberg,who
was not officially involved in the accident investigation,
Table 1. Major Explosion Accidents Contributing to Safety Science
Year
Location
Kind and amount
Consequence estimate
1920
Stolberg
(1,2)
AN,all induced by
blasting
25 t AN,
4500=750 t AN þ sulfate
Civil explosion
19 died,23 injured
561 died, >1991 injured
1921
Kriewald
(1,2)
1921
Oppau
(1,2,5)
1942
Tessenderloo,Belgium
(1)
150 t AN,the same as in Oppau
happened
100 killed
1944
Port Chicago,USA
(4,7)
2100 t ammunition
320 killed,390 injured
1947
Texas City (2 x)
(4,8)
2300=962 t AN
Fire)explosion
450 died,4000 injured
1967
<John Forrestal>
(4)
Fire)explosion
134 killed,162 injured
1899-
Many Chlorate explosions
(10,11)
Fire)explosion
also mechanical impacts
Many victims,serious damages
298 C.-O. Leiber and R. M. Doherty
Propellants,Explosives,Pyrotechnics 26,296–301 (2001)
4. Regulations
5. Case Histories of Non-Chemical Based Explosions
(Physical Explosions)
Explosives safety has been evaluated by accidents that
have occurred. All these experiences have been con-
densed into rules and laws describing what is proper
and what is not. Since the railways were the first motor
of progress,these early experiences have been interna-
tionally written into legal rules for transportation,which
still apply today. These rules have also been adopted
successively by other responsible agencies,which added
their own points of view. Contrary to the classical
explosives regulations,which prescribed the means of
achieving safety goals,the modern approach in nuclear
and chemical safety regulations is to set general legal
goals for safety and leave the means of achieving them to
be determined. Nevertheless all regulations have not only
a real scientific and=or technical basis,but also many
other combined interests,may be from practicability or
from economic interests. Therefore,the regulations also
differ,sometimes greatly,depending on the interests of
the user.
An early answer for safe distances was given by the
New Jersey tables of distances with respect to storage and
manufacturing. Whereas the old New Jersey and German
distances,based on actual accidents,used larger distances,
the later NATO distances were reduced according to a
reasonable risk with respect to defense
(24)
.TheK-
5.1Nature
3
p
½in kg; where D
is the distance in meters,and m is the applicable weight of
explosive (TNT) in kg. Whereas the NATO-criteria
expect a safe distance at K¼ 22.2 for a normal house,
K¼ 55.5 for hospitals and other most sensitive buildings,
we know from real accident experiences (Port Chicago,
1944) that the limit for injured persons can be K¼ 157,
and that of glass fracture K 300. One reason for this is
that in the military,field damage criteria are in use. But it
cannot be concluded that at distances beyond ‘‘a guaran-
teed damage level’’ safety is present. Since tables of
distances cannot be easily evaluated in a civil world,the
NATO-table of distances was adopted in many civil
regulations as a scientific result.
Regulations can also have an adverse effect on safety.
The density of regulations by various responsible agen-
cies has increased to such an extent,that it has now
become easy to attribute an accident that occurs to the
violation of a rule,and more detailed explorations are
often not felt to be necessary—to the detriment of real
safety.
Another misleading input both from theory (piston
model of detonation) and the regulations is the definition
of an explosion as the consequence of the gas production
rate by a chemical decomposition. This definition erro-
neously suggests that only chemically reactive substances
can be sources of explosion hazards. Due to this definition,
more general explosion hazards have been completely
excluded from any safety considerations. But there are
many examples of explosion hazards that do not involve
chemical decomposition.
All over the times celestial bodies impacted the earth with
gigantic effects,where the explosion by itself was not the
most serious. As example,in 1994,the impacts of parts of
Shoemaker-Levy on Jupiter demonstrated such events from a
safe distance,where the impacts on Jupiter resulted in
‘‘craters’’ of the dimensions of the earth.
The Tunguska-Event demonstrated,that such celestial
body impacts should be taken into considerations for risk
studies. So in 1908 a celestial body (probably a meteor) with
an estimated size of 30 m in diameter and a velocity of
between 50 and (near the surface) 3 km=s destroyed about
1200 km
2
of the Siberian taiga. The pressure waves were
recorded even in Germany.
As models for the nuclear winter volcanic explosions have
been considered in the past. Within historical times the most
powerful event had been 1815 with the Tambora eruption of
about 150–180 km
3
,and Krakatoa in 1883 with ‘‘only’’ about
18 km
3
erupted mass. It is a characteristic of such events,that
the number of immediate victims can be (as in the case of
Tambora) of the order of 12 000,but in time this number
increased to much more than 80 000 due to famine in the
immediate neighborhood,and much more all over the world.
Many social changes—positive and negative—resulted.
As a natural forerunner of industrial explosions appear the
Crater Lake Formations,where hot magma interacts with
water. Powerful steam explosions result in the formation of
crater lakes (German word: ‘‘Maare’’,creation about 30 000
years ago). In the spring 1977,the formation of two such
crater lakes within 11 days was observed in Alaska (Ukinrek
crater lakes).
5.2 Industrial Catastrophes
Classical examples of industrial physical explosions are
cavitating hydraulic Joukowski shocks,the fuel=liquid inter-
actions (FLI),which are more commonly known as vapor
explosions. These appear in many types of industry,such as
manufacturing of cellulose,oil industry,foundries,power
stations,explosions of hot cinders,in chemical processing,
by fire extinguishing,and most often in the kitchen. The most
catastrophic case is in nuclear reactors.
Explosion probabilities could not be determined until
nuclear reactor safety claimed the numerical evaluation of
the probability of such a risk for the first time. What was the
procedure? They defined that any vapor explosion is caused
by a melt fragmentation only
(25)
. This was also brought into
an official definition of a physical explosion
(26)
. An estimated
probability of an explosion was attributed to a given core
meltdown. Then,as a solution,the risk of a core meltdown is
quantitatively downcalculated. It is therefore a real matter of
safety science to verify or disprove such a masterpiece since
up to now explosion risks had been quantified only in the
factors are defined as K ¼ D ½in m=
m
Propellants,Explosives,Pyrotechnics 26,296–301 (2001)
Review on the Assessment of Safety and Risks 299
nuclear branch,but never in the fields of industrial explosions
and even not in explosives safety. The following case
histories demonstrate that this criterion is not adequate.
Explosions occur also without any fragmentation.
exploding monergol tanks is around 2 GPa at the low end
(LVD),and more than 10 GPa at the upper end.
5.2.4 Explosion of Liquid Carbon Dioxide Tanks
5.2.1 Hydraulic Transients
It was therefore ‘‘luck’’ that in the past several explosions
occurred with liquid pressurized carbon dioxide vessels
(1.5 MPa, 30
C),well below the superheat limit. These
accidents are of value for the following reasons:
The superheat theory is invalidated.
Furthermore,according to the Mollier phase diagram,
with isenthalpic depressurization to atmospheric pres-
sure,at 0.52 MPa,50 weight % of the carbon dioxide
condenses to ‘‘dry ice’’ (i.e.,solid CO
2
). Therefore,any
hypothetical propelling gas phase is drastically reduced.
By simple shock wave considerations one gets from the
maximum detected fragment width of 350 m in this case a
condensed phase pressure of the order of 700 MPa,which
is attributable to an explosive event.
Hydraulic transients are well known as Joukowski shocks,
but if these are cavitating,a powerful pressure augmentation
can take place. An improper release of water in the Tarbela
dam,1974,Pakistan,resulted in a powerful explosion.
5.2.2 Vapor Explosions
5.2.2.1Quebec Foundry Accident
45 kg molten steel of 1560
C dropped into 295 l water. By
calculation only 16 l water evaporated,but the explosion that
occurred had the effect of about 5.4 kg TNT. Cratering and
explosive devastation were observed,and up to 53 m away
brick walls were affected; more than 6000 windows were
broken
(27)
.
It is unlikely that this is the result of evaporated water
driving a pressure piston. Even if 1 cm
3
water is evaporated at
constant volume,at 1200
C only 7.325 bar can result
þ
,far
from any cratering capability.
Without any chemical reaction,such types of explosions
can occur spontaneously (Brooklyn,1971,liquid oxygen
accident),by weak mechanical impacts (or even in their
absence) as in marshaling,or by stronger impacts like derail-
ment,and finally by external fires as for example the Crescent
City,and Challenger
(32)
,1986,events demonstrate. Some-
times there are observed indications of build-up to such an
explosion: unusual noises in the tank,or repeated safety valve
clearances,but this is no reliable rule.
The dimethyl ether accident in Ludwigshafen
(33)
(1948)
demonstrates that there may also be political aspects of
explosive accidents. A witness saw that the tank car dis-
mantled,and after the sudden and violent dispersion of the
contents a room explosion followed,causing widespread
devastation,207 victims,3800 injured people,damages at
3200 buildings,and 9450 flats. After World War II it was
rumored—even from explosives authorities—that Germany
again was working on miraculous explosives. It was lucky
that an international committee,with such prominent
members as Straßmann (nuclear researcher),Professor
Richard,Nancy,and mining engineer Stahl,Washington,
testified that the explosion was not the result of a super
explosive. But they did not recognize the reason,and
speculated on a thermal overfill,and a concatenation of
misfortunes,ignoring thereby very similar accidents before
(1943). Other accidents of the same type followed therefore.
5.2.2.2 Reynolds Metal Co., McCook, USA, 1958
Moist or possibly wet scrap aluminum was inserted in a
melting furnace. An explosion caused 6 victims,and 40
injured. The damage was of the order of 1 million US$
(28)
.
This accident shows,that the explosion damage does not
correlate with the mass of the water that can be evaporated.
5.2.3 ‘‘Boiling Liquid Expanding Vapor Explosions
(BLEVE)’’
Liquid (pressurized) gas explosions of any kind (LNG,O
2
,
NH
3
,CH
4
,C
2
H
6
...,vinyl chloride,etc.) demonstrate best,
that a fragmentation process is not required for any explosive
event. A foaming up (by superheat in the case of a depressuri-
zation) and=or evaporation=condensation- or sorption=
desorption-resonances activated by mechanical means
(shaking of a champagne bottle) or thermal transfer processes
is postulated to be the cause. Since Rayleigh we have known
that the pressure in the condensed phase of a collapsing
cavity is of the order of 2 GPa. But current accident
investigations have concluded,erroneously,that the highly
increased gas pressure ruptures the vessel at the site of any
(assumed or real) embrittlement,and induces fragments. The
evaporated gas would propel the relatively large fragments,
which travel an increased distance by virtue of the aero-
dynamic lift
(29–31)
.
This view is invalidated by comparing the fragment
distances and fireball-diameters and -durations (in the case
of combustible gases) with exploding monergol tanks,which
are approximately the same. The order of the pressure of
5.2.5 Shocks in Silos
For powdered solid materials silo-shocking appears to be
the equivalent of the bubble resonance explosions of liquids.
This can be produced by a sudden breakdown of so-called
‘‘silo bridges’’ if a silo is being cleared. An explosive silo
rupture can result,predominantly if the grains are very
uniform in size. In performing the Low Velocity Detonation
studies on neat chlorates,experiments were also carried out
on salt (sodium chloride) of very uniform grain size,and sand
of varying grain sizes. The result was that the shock driven
compaction of salt dented a lead ingot,whereas sand did
þ
Kindly Dr. Volk,ICT,calculated these values.
300 C.-O. Leiber and R. M. Doherty
Propellants,Explosives,Pyrotechnics 26,296–301 (2001)
not
(17)
. Examples of bubble resonance explosions are given
in Table 2.
The Nios Lake (Cameroon) contained about 4 m
3
of
dissolved CO
2
per m
3
water. It was estimated,that in 1986
150 10
6
m
3
CO
2
explosively degassed,and still 250 10
6
m
3
remained in the water. Further explosive degassing occurred
with methane (Kivu Lake,Monoun Lake,1984,Tanganjika
Lake,all in Africa,and the Ocracoke in the Gulf of Mexico).
All these eruptions caused many victims by suffocation.
Another effect of degassing is that the original liquid’s
density decreases drastically by sparkling and foaming up,so
that a normal ship (built for normal water buoyancy) sinks
into this foam.
5.2.6 Rolling Over
Liquids of different densities (perhaps caused by different
temperatures of the same liquid,or different gas saturation,or
completely different and immiscible liquids) can be layered.
Such a situation can also result from an external fire,which is
extinguished. This is not a stable condition. The liquids can
suddenly mix by (an external) mechanical stimulus,or in the
case of different temperatures by thermal conductivity. It was
less well-known that above a critical difference in tempera-
ture,even after long times,a spontaneous onset of fluid
convection (Benard-convection) results. This can increase by
several orders of magnitude the thermal conductivity,so that
a whole system can be equilibrated within short times. The
result is that volatile products suddenly evaporate,and by
temperature balancing dissolved gases degas in the liquid. An
explosive foaming up,creating damage like explosions,is
then possible. But all degrees between quasi-static and highly
dynamic events are commonly observed. Examples are given
in Table 2.
6. Conclusions
A great number of victims of explosive accidents have
accumulated over the centuries. The most spectacular
numbers resulted from unforeseen or unexpected explosions.
(A rough estimate from explosion hazard studies indicates
that about 1% or less of all explosion accidents resulted in
about 70% of all victims.) These appear therefore as ‘‘low
probability—high risk’’ explosive phenomena,which are
completely outside of the present scientific considerations.
It seems outmost likely that the understanding of the nature of
explosions is not adequate. In the following article ‘‘Physical
Model of Explosion Phenomena’’ this question is focussed in
more detail.
Our personal conclusions are that even if there was a
predictive capability for all of these types of explosive
hazards,there exist real limits to the size of explosive
incidents of which the catastrophic consequences can be
managed,controlled,or avoided.
5.2.7 Spontaneous Degassing
Tectonic gases can dissolve in any kind of water,where
their solubility depends on the static pressure. In the deep
water the gas concentration is highly increased compared to
the surface layers,and the density reduced,so that a
(gradually) layering results. Mass transfer can be started by
any mechanical or thermal instabilities,which can lead to a
spontaneous,even explosive,degassing
(36)
.
Table 2. Examples of Bubble Resonance Explosions
7. References
LNG-tanks
Cleveland,Ohio (1944),La Spezia
(1) G. S. Biasutti,‘‘History of Accidents in the Explosives Industry’’ ,
Vevey,published by the author; J. Pointner,‘‘Im Schattenreich
der Gefahren’’,Int. Publikationen,GmbH,Wien,1994.
(2) R. Assheton,‘‘History of Explosions on which the American
Table of Distances was Based’’,Bureau for the safe Transpor-
tation of Explosives and other Dangerous Articles,The Institute
of the Makers of Explosives,1930.
(3) L. Spencer,‘‘Explosive Lessons’’,Hazardous Cargo Bulletin,
20–21 (November 1980).
(4) I. M. Korotkin,‘‘Seeunf¨lle und Katastrophen von Kriegschif-
fen’’ (5th ed.),Brandenburgisches Verlagshaus,Berlin,1991.
(5) H. Kast,‘‘Die Explosion von Oppau am 21. September 1921 und
die T¨tigkeit der Chemisch-Technischen Reichsanstalt’’, Son-
derbeilage zur Zeitschrift f¨r das gesamte Schieß- und Spreng-
stoffwesen 20, (1925) and 21 (1926); ‘‘Bericht des 34.
Untersuchungsausschusses zur Untersuchung der Ursache des
Ungl¨cks in Oppau’’, Zeitschrift f
¨
r das gesamte Schieß- und
Sprengstoffwesen 19,42–46 and 60–63 (1924).
(6) L. Spencer,‘‘An Act of Self-Mutilation’’,Hazardous Cargo
Bulletin (April 1981) pp. 25–26.
(7) ‘‘The Port Chicago, California, Ship Explosion of 17 July 1944’’ ,
Technical Paper No 6,(1948),Army-Navy Explosives Safety
Board,Washington,DC,USA.
(8) G. Amistead,‘‘The Ship Explosions at Texas City, Texas on April
16 and 17, 1947 and their Results’’,Report to John G. Simmonds
& Co Inc.,Oil Insurance Underwriters,New York City (1947);
Liquid gases of all kind
LNG,O
2
,NH
3
,CH
4
,CO
2
,
propane...,vinyl chloride....
External fire
Propane,Crescent City,1970
After extinguished
external fire
By mechanical impacts
By mechanical rupture
of the vessel
Butyl alcohol,Litchfield,1967
Vinyl chloride,Sch ¨nebeck,1996
NH
4
,Crete,1969
CO
2
,Haltern,1976
Apparently spontaneous
Oils
Shell-Pernis (1968) (mechanism
first evaluated)
(34)
Triest,Oil tank sabotage,1972
Tacoa,Venezuela,1982,many
victims: Burning oil erupted like
from a volcano,and distributed
fire simultaneously over a large
area
(35)
Tectonic CO
2
in a lake
Tectonic CH
4
in a lake or sea
Nios Lake,great amounts
of explosively deliberated carbon
dioxide produced about 2000
victims,and many animals died
by suffocation
(36)
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