Journal of Scientific & Industrial Research
Vol.59, June 2000, pp 455-459
Nontoxic/Environmentally Acceptable Pyrotechnic Smokes
Amarjit Singh, P J Kamale and Haridwar Singh
High Energy Materials Research Laboratory, Sutarwadi,
Pune 411 021
The pyrotechnic smokes have several applications , both in civil and defence fields. In the recent past, nontoxic and environmentally
acceptable smokes have gained importance because of increased awareness regarding the need to have a healthy environment, free from
toxic pollutants. The paper reviews nontoxic, environmentally acceptable smokes and suggests future line of work in this area.
Introduction
Pyrotechnic smokes, constitute an important class in
the field of pyrotechnics, wherein the heat of chemical
reaction between oxidant and fuel vaporises the volatile
ingredients or the products, which subsequently condense
as fine particles creating smoke 1-3 • The pyrotechnic
smokes are used in civil and defence sectors . They are
used for signaling, screening, decoying, deceiving, and
training purposes in the defence 4 -6 . Civil applications
include testing leakage in enclosed areas like boilers and
pipes, as insecticides, as a scavenging agent, for protection of orchards from sudden temperature changes, and
for putting off underground fires 7- 111 • Because of increased awareness and concern about the environment,
health and safety of living beings in recent times, many
studies are going on in India and abroad for the development of nontoxic and environmentally acceptable pyrotechnic smokes for fire-fighting, troop training, signaling and screening. In view of the scanty information
available in literature, a need was felt for a review of
the work done so far. This paper presents the survey of
the nontoxic/environmentally acceptable pyrotechnic
smo~e compositions.
Smoke Compositions
A nontoxic signal smoke was developed by mixing
40-80 per cent of potassium perchlorate with 5-30 per
cent iron, silicon, magnesium or aluminium powder 11•
A nontoxic bluish white smoke was generated by ignition of smoke composition containing 75 parts of potassium perchlorate with 22 parts of iron powder. Another
Japanese patent 12 describes the smoke generator, which
produces nontoxic smoke, containing the heating agent
manganese dioxide 52-80 per cent, iron oxide 10-20 per
cent and aluminium 10-20 per cent and packed in the
inner side of a metal cylinder with smoke generating composition containing paraffin 15- 90 per cent, sodium bicarbonate 10-50 per cent placed in the outer side of the
heating agent. The Americans have produced neutral
smoke (with pH 5-7) using the smoke composition zinc
oxide 29-33 per cent, polychloroisoprene 10-17 per cent,
ammonium perchlorate 31-40 per cent, ammonium chloride 3.8- 14.3 per cent, and dioctylphthalate (plasticiser)
6-12 per cent. The pressed pellets were coated with a
surface stabilising methacrylate resin and synthetic rubber, and had a burning rate of 0.9 mrnls 13 . Smoke producing liquid like titanium chloride (> 40 per cent of
total smoke charge) has been absorbed in a porous highly
absorbent powder containing activated carbon (bulk density< 0.7 and pore surface> 120m2/g) or volcanic ash
or calcium silicate. This mixture is useful as a smoke
charge for grenades, projectiles, rockets or bombs 14 •
An American patent 15 describes the nontoxic smoke
composition useful for fire fighting training, containing
cinnamic acid 47 .5, sucrose 12, potassium chlorate, 29,
sodium bicarbonate 6.5, and silicon dioxide 5 wt per cent.
The Germans 16 claim that a smoke composition of lower
toxicity can be produced by mixing guanidine nitrate 36
per cent, hexachloroethane 34 per cent, zinc 22 per cent
and zinc oxide 08 per cent or hexachloroethane 4 per
cent, red phosphorous 56 per cent, guanidine nitrate 40
per cent and believe that lower toxicity is due to
neutralisation of acidic products by guanidine nitrate.
A Polish patent 17 contains 14-29 guanidine nitrate or its
amine derivatives, 24-39 ammonium perchlorate, 2-6 .5
potassium chlorate, 0.5-2.5 potassium chromate, 23-37
anthracene, 5-36.5 polystyrene and 0.8 wt per cent ammonium chloride along with catalytic amounts of potas-
456
J SCI IND RES VOL 59 JUNE 2000
sium phosphate. The smoke generating agent is a mixture of anthracene, fine powdered polystyrene and sodium chloride. A smoke composition containing ammonium chloride 50g, sugar 25 g, potassium chlorate
20 g, and alizarine dye 5g has been used for leak detection in chimneys and for other flow control investigations18. Another Dutch patent 19 describes smoke composition containing ammonium chloride 56 per cent,
white sugar 15 per cent, rosin 9.5 per cent, and potassium chlorate 19.5 per cent packed in a polyethylene
bag which produces smoke that is an environmental and
health improvement and is useful for testing leakage in
pressure systems. A German patent20 uses a mixture of
polyethylene glycol (average molecular weight 200-600)
and water in 1:9 or 9:1 volume or wt per cent ratios for
smoke screens, which can be used for obscuring military installations without endangering friendly personnel. Glycerine can also be used in place of polyethylene
glycol. Helbig and Anders 21have used 1,2-propanediol
70-90, water 10-30, ethanol 0.2 and an odor masking
substance 0.001-0.004 vol per cent for producing white
theatrical stage smoke by heating and spraying the liquids. The Americans 22 have used BAMO [3,3 bis(azidomethyl) oxetane] as fuel for flares and colored
smokes, which helps in greater ship and aircraft safety.
Swiatosz23 has described the method of generating training smoke using propylene glycol PEG 200 or PEG 200water mixture. An American patent24 claims that nontoxic smoke can be produced from a smoke composition
consisting of 1,4 benzene dicarboxylic acid 50, potassium chlorate 23, and sucrose 27 wt per cent. Another
German patent25 claims that nontoxic smoke screens
consisting of sodium chloride or potassium chloride particles can be generated by .a composition consisting of
magnesium 10-25, potassium nitrate 20-36, potassium
perchlorate 0-15, calcium carbonate 12-20, potassium
bicarbonate, sodium bicarbonate, potassium carbonate,
and/or sodium carbonate 0-10, potassium chloride/sodium chloride 20-50 and azodicarbonamide, oxamide or
dicyandiamide 5-20 wt per cent. The priming composition for this is a mixture of magnesium powder 25, potassium nitrate 10, potassium perchlorate 10, calcium
carbonate 20 and potassium chloride 10 wt per cent.
Uwe 26 of NICO Pyrotechnic Germany, has produced a
nontoxic smoke composition called KM which contains
potassium chloride 44 per cent, potassium perchlorate
5 per cent, potassium nitrate 27 per cent, magnesium 8
per cent, and azodicarbonamide (H N-CO-N =N-CONH ) 16 per cent. The aerosol genJ rated contains particiJs of sublimed potassium chloride, potassium compounds and magnesium oxide which are nontoxic and
have pH between 7.0- 8.0. The ignition composition
contained potassium nitrate 63 per cent and magnesium
powder 23 per cent, while the booster composition consisted of potassium nitrate, 47 per cent, calcium carbonate 21 per cent, and magnesium 32 per cent. It is claimed
that a residue of only 15 per cent is obtained which consists of potassium chloride, potassium carbonate, and
magnesium oxide. An American patent27 claims that
white smoke generator for use in military screening contains terephthalic acid 35-65 wt per cent and 3,3-bis
(azidomethyloxetane) energizer and produces nontoxic
smoke. By thermal nebulization process, nontoxic smoke
has also been produced using 1,2 propanediollwater mixture2x. American scientists have produced nontoxic
smoke using aliphatic dicarboxylic acids, binder, oxidant, fuels, and coolants. However, full details of ingredients used are not given in this patent2 9 . Waltor and
Tobler30 , in their patent, describe an environmentally safe
smoke generating pyrotechnic composition which uses
porous carbon granules (organic reducing agents) and
ammonium nitrate (inorganic oxidising agent). The
oxidising agent is bound to carbon granules by using a
polar solvent. It is also reported that the M8 smoke pot
For biodata of Dr Am arjit Singh and Mr. P J Kamale, see 1 Sci Ind Res, 57(3 ) ( 1998) 124.
Dr Haridwar Singh is a Director in High Energy Materils Research Laboratory (HEMRL), Pune. He
obtained his Ph.D. in Solid Rocket Propellant Combustion from University of Pune. He has supervised 20
post-graduate and doctoral thesis. He was a Visiting Scientist at the Max-Plank Institute, Germany; High
Pressure Combustion Laboratory, Pennsylania State Uni versity, Army Research Laboratory; Maryland Science Application Centre. Santa Clara and Sandia National Laboratory, USA. He was awarded the Astronautical Society of India Award f or the year 1994. He was conferred with the DRDO Scientist of the Year
Award in 1983 and 1993 f or his contributions in applied sciences and advanced solid propellants, high
energy propellants, respectively. He is the recipient of DRDO Cash Award for development of power plants
for missile target and Best Paper Award of Defence Science Journal in 1984. He is the Chairman of th e
High Energy Materials Society of India, a member of AIAA, International Advisory Board-Flame Structure
& Combustion, and honorary member of the Russian Academy of Astronautics.
SINGH et al.: PYROTECHNIC SMOKES
containing benzene and formaldehyde are currently the
safest training pot used by the US Army, along with
terephthalic acid based smoke composition 3 1. An American patent claims that a smoke composition for training
fire fighters in extinguishing fires contains ferrocene and
its derivatives, along with a volatile iron compound,
which can be incorporated in the liquid hydrocarbon 32 .
A nontoxic coloured smoke generating composition described in a Japanese patent contains sodium azide 2023 per cent, smoke controlling agents 5-I5 per cent, dyes
45 --55 per cent, coolants 0 - I5 per cent, and binders 0
- 12 per cent13 . Shidlovskiy 34 desc ribes another nontoxic smoke composition based on ammonium chloride
and containing potassium chlorate 20-30 per cent, ammonium chloride 50 per cent, naphthalene or anthracene
20 per cent, and wood charcoal 0 - I 0 per cent. Ammonium chloride based nontoxic smoke composition has
also been developed in India and used in the training
smoke generator 35 .
Amarjit Singh et al. 36 have determined theIR screening properties of a nontoxic smoke composition containing I5 per cent anthraene, 40 per cent potass ium chlorate, and 45 per cent ammonium chloride in the IR windows 2-2.4 11m, 3-5 11m and 8-13 11m along with theIR
emi ssion characteristics of the smoke cloud of 4 .9 11111
and 10.6 11m. In addition the particle size of the same
nontoxic smoke composition has been determined by
Amarjit Singh et a!Y using Andersen Fractionating sampler and the aerodynamic median diameter (AMD) was
found to be 0.82 11m while the geometric standard deviation (<J g) was 1.23 11m.
Turetsky and Young 3 x have carried out study for safe
and efficient sc reening smoke compositions and have
concluded that the compos itions like (i) Terep hth alic
acid, 57 per cent, sucrose 14 per cent, potassium chl orate 23 per cent, magnes ium carbonate 3 per cent, grap hite 1 per cent and nitrocellulose 2 per cent, (i i) Mi crocrystalline Mekon white 36.5 per cent, potassium chl orate 34.8 per cent, sucros(! 18.7 per cent, diatomaceous
earth (ce llite) 5.0 per cent, sodiu m bicarbonate 5.0 per
cent, (i ii ) Sulphamic ac id 58 .0 per cent, ammonium perchlorate 42.0 per cent, (iv) Red phosphorus 40.0 per
cent, manganese di oxide 32. 1 per cent, magnesium 8.8
per cent, zinc ox ide 3.0, linseed oil 2.9 per cent, and
potassium chloride 13.2 per cent, (v) Red phosphorus
40 per cent , manganese dioxide 32.1 per cent, magnesium 8.8 per cent, zinc ox ide 3.0 per cent, linseed oi l
2.9 per cent and sodium bicarbonate 1.3 per cent, and
(v i) Orthophosp horu s acid 80.0 per cent, ammon ium
. 457
perchlorate 20.0 per cent are potentially useful as en vi- .
ron mentally acceptable compositions. Smoke compositions, based on potassium chlorate, lactose, and 20-45
per cent cinnamic acid are used by the British forces for
screening, fire fighting and riot training.JY Hancox and
Murphl 0 have discussed the essential requirements of
the training smoke and stated that the system based on
titanium tetrachloride, flaky materials (like graphite and
iron oxide) along with pyrotechnic smokes based on
white dyes (like methyl anthraquinone a nd
chloroanthraquinone) as well as cinnamic acid and
terephthalic acid (mixed with chlorate and lactose) have
good potential for training smokes. In Australia, white
smoke compositions based on terephthalic acid and cinnamic acid are being developed for fire fighting trai ning
in enclosed areas 41 • A castable composition with burning time of 5 min and mass 1.2 kg has been developed in
Canada, which contains cinnamic acid 50 per cent, potassium chlorate 23 per cent, sucrose 6 per cent, iron
oxide 1 per cent, and binder (hydroxy termin ated
polybutadiene) 20 per cent. The combustion products
from this composition have also been deterrnined 42 . Work
was carried out in America to replace hazardous colour
dyes used in the MIS colored smokes hand grenades.
Vat yellow 4 and benzanthrone used in the yellow smoke
composition were replaced by Cl solvent yellow 33 to
give the yellow smoke composition containing potassium chlorate 22 per cent, sucrose 15 per cent, magnesium carbonate 2I per cent and CI solvent yellow 33 (42
per cent). Similarly, environmentally acceptable green
smoke composition used in the grenade contained chinoline yellow S 12.5 per cent, solvent green 3 (29 .5 per
cent), magnesium carbonate I7 per cent, potassium chl orate 25.5 per cent, and sucrose 16.5 per cent. Acti on
was also initiated to repl ace hexachloroethane, zinc oxide and aluminium smoke mixture used in M8 grenade
and M5 smoke pot, by smoke composition containi ng
red phosphoru s 51 per cent, magnes ium 10.5 per cent,
manganese dioxide 32 per cent, magnesium oxide l .5
per cent, and microcrystalline wax 5 per cent43 .
Smokes for Future - A Scenario
T he future development of screenin g, signa lin g,
and trai nin g smokes woul d involve composi tions whic h
produce products that are biodegradable or are nutrients for the soil or are chemicals which do not harm th e
environment. For signaling composition, there wou ld
be a trend to use dyes which are used in food stuffs and
pharmaceutical s and hence are nonpolluting and harm-
458
J SCI IND RES VOL 59 JUNE 2000
less, or those which get decomposed subsequently into
harmless products by the action of light, water, and microorganisms.
Conclusions
References
I
2
The various nontoxic, environmentally acceptable
smoke compositions can be classified under six main
groups:
3
(i)
4
Smoke compositions generating volatile chlorides
of alkali metals like sodium chloride, potassium
chloride or least amount of zinc chloride 1L25 .26·3x. For
the smoke compositions producing zinc chloride the
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m 3 and the intravenous lethal dose for 50 per cent
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chloride and potassium chloride are nontoxic chemicals44-4s.
(ii) Smoke compositions generating particles of alkaline oxides and chlorides like calcium hydroxide,
magnesium oxide, calcium carbonate, and ammonium chloride act as nutrient for plants and are,
therefore, environmentally acceptable 25-26 .
(iii) Use of suitable agents for neutralisation of acidic
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acid,
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acid 12,15,24,27,29.31.3H.39,40-42. These compounds and their
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as well as food preservatives, and are at the most
mild irritants 47.
(v)
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and also use of white dyes like methyl anthraquinone40-43. The anthraquinone compounds are
reported to have low toxicity4 7.
(vi) Use of Red phosphorus based compositions in place
of smoke compositions containing hexachloroethane, zinc oxide and aluminium as red phosphorus,
is a relatively low human health hazard 16.3R.43 .
The various nontoxic environmentally acceptable pyrotechnic smokes have a very bright future in the national and international civil and defence sectors. Many
newer smoke compositions will be developed to meet
the demands of the millennium.
5
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47
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Six lee nlh