Chapter 28: Gas and Fume Generation at the Blast Site

TOXICITY LEVELS

As previously mentioned, the toxic gases of primary concern for blasting operations
are NO, NO,, and CO. One common way to express the toxicity of these gases
is the OSHA Permissible Exposure Limit or PEL. The PEL is the time weighted
average concentration, usually expressed as parts per million (ppm), that must not be
exceeded during an 8 hour work day. The PEL for NO,, NO, and CO are 5, 25, and
50 ppm, respectively (NIOSH, 1994). Toxicity of gases may also be expressed as the
concentration Immediately Dangerous to Life and Health, or IDLH. Workers should
never be exposed to concentrations above the IDLH without specialized respiratory
protection. The IDLH levels have been set based on the belief that a worker would
be able to escape to fresh air without loss of life or irreversible health effects. The
IDLH for NO,, NO, and CO are 20, 100, and 1,200 ppm, respectively (NIOSH,
1994),

The only reliable way to detect the presence of toxic gases following a blast is
with an instrument designed to detect these gases. These instruments may be used
to monitor the gases being released by a muck pile or determine whether the air in
a confined space near a blast is safe to breathe.

CONFINED SPACE

The National Institute for Occupational Safety and Health (NIOSH) defines
a confined space as “a space which by design has limited openings for entry and
exit, unfavorable natural ventilation which could contain or produce dangerous
air contaminants, and which is not intended for continuous employee occupancy”
(See NIOSH web site). An example of a confined space near a construction blast
might be a manhole or an excavation for utility lines. The Occupational Safety and
Health Administration (OSHA) guidelines for confined space safety should always be
followed since a dangerous atmosphere may result from many sources in additions to

blasting (See OSHA web site). Figure 28.3 shows a worker using a multi-gas monitor
to measure blasting fumes in a manhole. on a trenching project.

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TOXIC HAZARDS OF CO, NO, AND No,
CO is an odorless, colorless gas that can cause illness and death by asphyxiation. In
general, the first symptoms include headache, fatigue and lightheadedness. At high
exposures to CO, skin flushing, rapid heart rate, and lowered blood pressure occur. At
even higher exposure levels, decreased attention span is followed by nausea, vomiting,
impaired coordination, fainting, coma, convulsions, and, finally death.

NO isa colorless gas. Symptoms of exposure include redness of the eyes,abdominal
pain, coughing, headache, dizziness, blue skin, lips, or fingernails, shortness of breath,

and convulsions. Exposure to NO will always include simultaneous exposure to NO,
since NO is continuously converted to NO, in the atmosphere.

NO, is a brown gas with a pungent odor. It is very corrosive and will cause severe
burns to the skin, eyes, and lungs in sufficiently high concentrations. Symptoms
include a burning sensation to skin, eyes, or lungs, sore throat, cough, dizziness,
headache, sweating, labored breathing, nausea, shortness of breath, and vomiting. The
symptoms for NO, poisoning may be delayed. A person exposed to NO, may feel
only minor symptoms at first. The actual damage to the lungs may not show up
until several hours later, at which time the lungs become congested with fluid and
breathing becomes labored.

The symptoms of CO, NO, and NO, exposure are similar to those of the flu
and other illnesses. People exposed to these toxic gases may think they are coming
down with a cold, the flu, or are suffering from food poisoning. Ifa worker becomes

ill on the worksite, it is a good idea to stay on the side of caution and seek medical

attention.

Blasters working in underground or confined environments have long been aware

of the hazards of these gases and know that they must ensure adequate ventilation
to quickly dilute them below harmful levels before returning to their work stations.
Blasters at surface mines and construction operations have not been as concerned
about blasting fumes as their counterparts in underground mines, believing that
fumes would be adequately dispersed in the open air (ISEE, 1998).
Surface blasters, however, must be aware that toxic fumes have the potential to
ate hazards in their operations. Some large surface mines detonate up to two
million pounds of blasting agent in a single shot. Some of these shots produce a
red or orange colored cloud, which indicates the presence of NO, (Barnhart, 2004),
(Barnhart, 2003), and (Lawrence, 1995) and is unsafe to breathe.

The CO in the gaseous products released immediately after a blast is not as much
of a concern as the NO and NO, since CO is much less toxic than NO and NO,.
The CO danger lies with the gas that remains in the ground after the blast which is
released to the atmosphere during loading operations or may migrate through the
ground and collect in confined spaces.

cr

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Figure 28.3 - Worker using a multi-gas monitor to measure blasting fumes in a manhole, on a trenching project.
(Courtesy: R. Mainiero)

CO MIGRATION
In rare cases blasting fumes may travel hundreds of feet through the ground and
collect in the basement of a structure adjacent to a blasting site. In these cases the
culprit is likely CO. NO and NO, do not travel far through the ground due to soil
and ground water absorption (Mainiero, 2007). CO, being odorless and colorless,
may build up in a basement or other confined space without any warning or telltale
odor. Since 1988, there have been eighteen documented incidents of CO migration
in the United States and Canada; the confined space typically being a home and in
one case a sewer manhole vault (NIOSH, 1998), (Eltschlager, Schuss, Kovalchuk,
2001), (NIOSH, 2001), and (Santis, 2001). There have been thirty-nine suspected
or medically verified carbon monoxide poisonings caused by blasting-generated
CO, with one fatality. In one incident in Kittanning, Pennsylvania, blasting fumes
traveled 450 feet from a coal strip mine into a home, poisoning a couple and their
baby. Fortunately, all three recovered following treatment in a hyperbaric chamber
(Eltschlager et al. 2001) and (NIOSH, 2001).

The only way to detect the CO is with an instrument. Fortunately many

homeowners have installed monitors to detect CO that may be produced by a faulty
furnace or space heater. These monitors work just as well in detecting CO that may
come from a blast. [fa home near a blast does not have CO monitors, a blaster should
consider giving or loaning the homeowner one for the duration of the blasting.

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Gas and Fume Generation
At the Blast Site

Gases and fumes are generated as a result of explosives detonation at a blast site.
This chapter discusses only those gases produced by the detonation of commercial
explosives. Since fracturing of the rock has potential to allow these detonation gases
to either (1) accumulate in the muckpile or (2) migrate out of the blasted area, they
should be ventilated as soon as possible.

Underground operations install ventilation systems to exchange the air, but surface
operations rely on natural ventilation to the open air. To facilitate the ventilation, the
blaster-in-charge should encourage early muckpile excavation to avoid any potential
of accumulation of detonation gases.

DETONATION GASES
The heaving action of an explosive is a result of the large quantities of rapidly
expanding hot gases produced as it detonates. Ideally, a detonation produces only
steam (HO), carbon dioxide (CO,), and nitrogen (N,) as a result of the reaction.
However, in the real world the detonation of explosives in a blasting operation also
produces the three toxic gases: (1) nitrogen dioxide (NO,), (2) nitric oxide (NO),
and (3) carbon monoxide (CO) (ISEE, 1998). The quantities of CO, NO, and NO,
released by the explosive varies according to conditions of use and its formulation by
the manufacturer.

Anything that tends to cool the detonation process increases the formation of

oxides of nitrogen. Some of the factors that increase toxic fumes are poor product
formulation, improper use, inadequate priming, insufficient water resistance, degree
of confinement, reactivity of the explosive ingredients with the rock or other material
being blasted, and incomplete product reaction, In general, poor performance of an
explosive in a blast tends to increase the production of toxic fumes. Fumes should not
be confused with smoke, which is composed mainly of steam and the solid products
of combustion or detonation. Excessive exposure to smoke, especially that produced

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Chapter 28: Gas and Fume Generation at the Blast Site

REFERENCES

Barnhart, C. R. 2004. Analytical measurements in cast blasting co identify the cause and cure for “orange smoke.”
International Society of Explosives Engineers (ISEE) Proceedings of the 30th Annual Conference on Explosives and
Blasting Technique, February 1 - 4 pp. 1 — 15, New Orleans, LA. ISEE, Cleveland, OH

Barnhart, C. R. 2003. Understanding the “orange smoke” problem in cast blasting. International Society of Explosives

Engineers (ISEE) Proceedings of the 29th Annual Conference on Explosives and Blasting Technique, pp. | ~ 11, February
2-5, Nashville, TN. ISEE, Cleveland, OH.

Mine Safety and Health Administration (MSHA). Code of Federal Regulations (CFR), Title 30, Section 15.20(g). MSHA
shington, D.C.

Eltschlager, K. K., Schuss, W., Kovalchuk, T: E. 2001. Carbon monoxide poisoning at a surface coal mine,
International Society of Explosives Engineers (ISEE) Proceedings of the 27th Annual Conference on Explosives and
Blasting Technique, January 28 ~ 31, Orlando, FL. ISEE, Cleveland, OH

A case study.

International Society of Explosives Engineers (ISEB). 1998, ISEE Blasters’ HandbookTM, 17th Edition,
p.48. ISEE, Cleveland, OH.

Karmakar, N.C. and Banerjee, S. P. 984. A review of laboratory and field test methods for studying fume characteristic of
explosives. Journal of Mines, Metals and Fuels,Vol. 32, No. 1/2, January ~ February pp. 398-402

Lawrence, D. L, 1995. A study of post blast generation of nitrogen dioxide. International Society of Explosives Engineers
(ISEE) Proceedings of the 22nd Annual Conference on Explosives and Blasting Technique, February 2
Nashville, TN. ISEE, Cleveland, OH,

3, pp. 1 12.

10, R. 1997.A technique for measuring toxic gases produced by blasting agents. International Society of Explosives
neers (ISEE) Proceedings of the 23rd Annual Conference on Explosives and Blasting Technique, pp. 595-604, February

Las Vegas, NV. ISEE, Cleveland, OH

Mainiero, RJ., Harris, M.L., and Rowland, JH. 2007. Dangers of toxic fumes from blasting, International Society of
:xplosives Engineers (ISEE) Proceedings of the 33rd Annual Conference on Explosives and Blasting Technique, January
28 — 31, Nashville, TN. ISEE, Cleveland, OH.

National Institute for Occupational Safety and Health (NIOSH). 2001, Technology News 488 - Migration of blasting
fumes into a western Pennsylvania Home, Pittsburgh, PA. US. Department of Health and Human Services, Public Health
Control and Prevention, National Institute for Occupational Safety and Health.

Service, Centers for Diseas

National Institute for Occupational Safety and Health (NIOSH). 1998. NIOSH HETA 98-0020, Hazard evaluation and
technical assistance report: Carbon monoxide intoxication and death in a newly constructed sewer manhole, Cincinnati,
OH.US rvices, Public Health Service, Centers for Disease
National Institute for Occupational Safety and Health,

‘ontrol and Prevention.

Department of Health and Huma

National Institute for Occupational Safety and Health (NIOSH). 1994. Pocket guide to chemical hazards. DHHS (NIOSH)
Publication No, 94-116, Cincinnati, OH. U.S. Department of Health and Human Services, Public Health Serv
for Disease Control and Prevention, National Institute for Occupational Safety and Health.

¢, Centers

Santis, L.D,,J. H. Rowland, III, D. J.Viscusi, and M. H.Weslowski. 1995, The large chamber test for toxic fiames analysis for
permissible explosives, International Society of Explosives Engineers (ISEE) Proceedings of the 21st Annual Conference
on Explosives and Blasting Technique, February 5 — 9, Nashville, TN, ISEE, Cleveland, OH.

Santis, L. D. 2001, A summary of subsurface carbon monoxide migration incidents, International Society of Explosiv
Engineers (ISEE) Proceedings of the 27th Annual Conference on Explosives and Blasting Technique, January 28 ~ 3
Orlando, FI.ISEE, Cleveland, OH

1,

Streng, A.G. Evaluation of Toxic After Detonation Gases Formed By Industrial Explosives, Explosivstoffe, 1971, vol. 34,
pp. 58-64

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by dynamite, can cause severe headaches and should be avoided. The headache may
be the result of small particles of unreacted or partially reacted explosive ingredients
in the smoke. Explosives manufacturers are able to provide products that minimize
to!
sufficient natural or forced ventilation may not be sufficient to dissipate the fumes.

> fumes production and should be consulted when blasting in locations where

In an effort to protect workers, extensive research has been done on the toxic

fumes generated by the detonation of explosives. Many countries have test procedures
and formal or informal requirements in place for the maximum permitted fumes
production by a given amount of explosives (Streng, 1971, Karmakar and Banerjee,
1984, and International Society of Explosives Engineers, 1998). In the U.S., the
system used for quantifying the toxic gases produced by an explosive is the Institute
of Makers of Explosives (IME) fume class. The IME fume classification is based on
the toxic gases produced by the detonation of a 32 millimeter by 200 millimeter (14
inch x 8 inch) cartridge of explosive in the Bichel Gauge (See figure 28.1).
Explosives producing less than 4.53 liters (0.16 ft’) toxic fumes are rated IME
fume class 1. IME fume classes 2 and 3 produce larger quantities of toxic fumes.
Blasters who wish to shoot blasting agents underground in a state requiring IME fume

class 1 explosive are faced with a dilemma. Blasting agents will not reliably detonate
at full order when initiated by a blasting cap as a 32 millimeter by 200 millimeter
(1% inch x 8 inch) cartridge so it is not possible to determine IME fume class using
the Bichel Gauge. Therefore, explosive manufacturers calculate fumes quantities
based on thermodynamics to assign fume classes for those products. Internationally,
measurements of the toxic fumes produced by blasting agents in large scale mining
operations have been conducted but these have been carried on as research and no
standardized test procedure has been developed. (Streng, 1971) (Mainiero, 1997).

Figure 28.1 - Bichel Gange used for determining the quantities of toxic gases released by
Courtesy: R. Mainiero)

a cartridge of explosi

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Chapter 28: Gas and Fume Generation at the Blast Site

In the USS., the U.S. Mines Safety and Health Administration has placed limits
on the toxic fumes that may be produced by permissible explosives for blasting in
underground coal mines. These are detailed in the U.S. Code of Federal Regulations
Title 30, Part 15 and are based on measurements made in the Large Chamber Test (See
figure 28.2). In this test, 0.454 kilogram (1 pound) of explosive is loaded unstemmed
in a cannon at one end of the chamber. Following detonation of the explosive, the
fumes in the chamber are sampled and analyzed. Based on the quantity and types of
toxic gases produced, the explosive is approved or rejected as a permissible explosive
(Santis, 1995).

Figure 28.2 - Large Chamber used for determining the toxic fumes produced by permis
(Courtesy: R. Mainiero)

ble explosives.

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