Toxic Fume Comparison
 

of a Few Explosives Used in Trench Blasting
 

By Marcia L. Harris, Michael J. Sapko, and Richard J. Mainiero
 

National Institute for Occupational Safety and Health Pittsburgh Research Laboratory
 

ABSTRACT 

Since 1988, there have been 17 documented incidents in the United States and Canada in which 

carbon monoxide (CO) is suspected to have migrated through ground strata into occupied enclosed 

spaces as a result of proximate trench blasting or surface mine blasting. These incidents resulted in 

39 suspected or medically verified carbon monoxide poisonings and one fatality. To better 

understand the factors contributing to this hazard, the National Institute for Occupational Safety and 

Health (NIOSH) carried out studies in a 12-foot diameter sphere to identify key factors that may 

enhance the levels of CO associated with the detonation of several commercial trenching explosives. 

The gaseous detonation products from emulsions, a watergel, and ANFO blasting agents as well as 

gelatin dynamite, TNT, and Pentolite boosters were measured in an argon atmosphere and compared 

with those for the same explosives detonated in air. Test variables included explosive formulation, 

wrapper, aluminum addition, oxygen balance, and density. Major contributing factors to CO 

production, under these laboratory test conditions, are presented. The main finding is the high CO 

production associated with the lack of afterburning in an oxygen poor atmosphere. Fumes 

measurements are compared with the manufacturer’s reported IME fume class and with the Federal 

Relative Toxicity Standard 30 CFR Part 15 in order to gain an understanding of the relative toxicity 

of some explosives used in trench blasting. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 2 of 18

INTRODUCTION 

Toxic gases such as CO and NO are produced by the detonation of explosives. The implications and 

minimization of such products have been studied for decades. Early research addressed toxicity 

issues associated with blasting in confined spaces such as underground coal mines. Over the past 

decade there has been an increased interest in the toxic gases that are released during some large 

surface mine blasts. More recently, the mining and construction industry has been concerned with 

toxic detonation products that may travel laterally through the earth rather than be vented to the 

atmosphere. Since 1988, there have been 17 reported incidents where explosive-generated CO 

moved through the earth and accumulated in nearby underground enclosed spaces.1, 2 Investigators 

could usually identify a probable pathway from the blast to the problem structure. Likely pathways 

included old trenches filled with porous material intersecting the blast site, horizontal sedimentary 

bedding, unconsolidated material in a horizontal plane, and hillseams together with sumps, drains, the 

gap between a basement floor and wall, and direct openings in structure walls. 

These reported incidents involved about 39 suspected or medically verified CO poisonings and one 

fatality. Santis1

 summarizes ten of the incidents that occurred in private residences and one that 

occurred in a manhole. In each case, overburden heavily confined the explosive in the blasts, 

restricting the venting of explosive gases to the atmosphere. All the blasts were in or near residential 

areas and none of the areas were excavated immediately. Five of the blasts were within 6 to 15 

meters (m) (20 to 50 feet [ft]) of the enclosed underground spaces, three were 30 to 46 m (100 to 150 

ft) away, and one was 120 to 150 m (400 to 500 ft) away. 

In open-pit blasting operations, wind rapidly dilutes the vented gases during the fragmentation 

process and continues to dilute the gases slowly emanating from the muck pile. Generally, trench 

blasting near occupied dwellings is done with heavy explosive confinement with a focus on 

preventing fly rock and minimizing air blast damage. Consequently, there is little to no surface heave 

or venting for most of the shots. Most investigations of these incidents identified CO from outdoor 

blasting operations which migrated through the earth into underground basements and enclosed 

manholes. Emergency responders reportedly detected CO at dangerous concentrations that were 

often initially attributed to malfunctioning furnaces or hot water tanks. 

The NIOSH Pittsburgh Research Laboratory (PRL) has initiated a study designed to compare the 

relative toxic fumes produced from the unconfined detonation of a few explosive types that have 

been used in some trenching operations. It is impossible to “simulate” all aspects of trench blasting 

or any type of blasting under laboratory conditions, including explosive confinement that might be 

expected in the field. Confinement can differ significantly in blasting operations as a result of 

variations in the strength of material blasted to variations in explosive loading density and borehole 

coupling. The degree of confinement can differ from shot to shot and with location, all of which have 

the potential to influence the resulting fume spectrum. The degree of explosive confinement can 

significantly influence fumes production with blasting agents since most blasting agents, by their very 

nature, require heavy confinement or very large diameter blast holes to reach the designed or 

maximum VOD. On the other hand, cap sensitive or molecular explosives used in this study, have a 

small critical diameter, detonate at about the same velocity either unconfined or confined in schedule 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 3 o

80 pipe. Therefore, the toxic fumes production should be less influenced by degree of confinement 

since the VOD is a good indication of reaction efficiency. 

The primary focus of this initial study is to compare the “relative level” of toxic fumes production of 

various explosives and initiators when detonated un-confined in an oxygen deficient atmosphere. 

Cap sensitive commercial explosives were compared on the same basis and these results may be 

considered as the “worst case” since any confinement should increase borehole pressure, temperature, 

and inter-molecular contact time leading to a conceptual reduction in toxic fumes. Also, depending 

on the explosive loading density, there may be some residual air in the borehole that may contribute 

to some limited secondary oxidation reactions of CO to CO2 and NO to NO2. 

In the reported incidents that occurred in the U.S., the types of explosives involved were TNT, 

ANFO, watergels, dynamites, emulsions, and some combinations of the same. Detonation studies 

were conducted in air and in argon (low oxygen) atmospheres to examine the relative differences in 

fumes production with and without the occurrence of post detonation oxidation reactions. The post 

detonation fumes measured in an argon atmosphere are assumed to more closely represent fumes 

produced from the detonation, while the resulting fumes from detonations in air include secondary 

oxidation reactions. 

This report presents the preliminary results of studies in NIOSH’s 12-foot diameter sphere to 

compare the toxic fumes production from the unconfined detonation of a few select trenching 

explosives and boosters in an oxygen deficient atmosphere. 

EXPERIMENTAL APPROACH 

Studies were conducted in NIOSH/PRL’s 3.7-m (12-ft) diameter 25.6-m3

 (905-ft3) sphere shown in 

Figure 1. The sphere is made of 1.7 cm (0.68 in.) thick steel walls with a pressure rating of 21 bar 

(300 psig). For ANFO tests, the pulverized (-60 mesh, < 250 microns) ANFO mixture was placed in 

a glass tube with a 4.45-cm (1.75-in) inner diameter, 0.15-cm (0.06-in) wall thickness, and 61-cm 

(24-in) length. Glass was chosen because it is inert and would not contribute to the fumes production. 

A cast Pentolite (PETN/TNT) (50/50) booster 2.5 cm (1 in.) thick and 5.0 cm (2 in.) in diameter 

(about 70 grams) was taped with minimal masking tape to one end of the tube. Prior to loading the 

glass tube with explosive, a continuous velocity probe of the type described by Lon Santis3

 was taped 

to the inner surface of the glass tube along its length. The glass tube filled with ANFO was 

suspended vertically in the geometric center of the sphere and initiated with a No. 8 copper blasting 

cap placed in the well of the booster. Cap-sensitive trenching explosive cartridges were evaluated as 

received from the manufacturer and were also initiated with a No. 8 blasting cap. 

To create an oxygen-poor atmosphere, argon was slowly introduced into the bottom of the sphere 

from a 230 L (8.12 cu. ft) dewar of cryogenic argon through a 0.95 cm (3/8-in.) copper tube. The air 

was slowly displaced through a 1.27 cm (1⁄2-in.) copper vent tube from the top of the sphere. Most 

tests were conducted when the average oxygen concentration was less than 1%. 

*

 Reference to specific products is for informational purposes and does not imply endorsement by

NIOSH. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

Following the detonation of explosives in the sphere chamber, one minute passed before the sample 

lines were opened. The fume samples were taken out of the chamber through 0.64 cm (1/4-in.) 

Teflon tubes for analysis. Teflon sample lines were used to minimize loss of nitrogen oxide 

constituents due to absorption on surfaces. Vacutainer*

 samples were taken at 10 minute intervals for 

60 minutes following detonation. Samples were sent to the analytical laboratory for gas 

chromatographic (GC) analysis. This technique was appropriate for components that remained stable 

in the Vacutainer, namely hydrogen, carbon monoxide, and carbon dioxide. Nitrogen oxides are not 

amenable to analysis by the Vacutainer technique and were instead analyzed on-line by gas analyzer 

instrumentation. Two electrochemical cell based gas analyzers, an Enerac 3000E*

 and a Testo 350*,

*

 Reference to specific products is for informational purposes and does not imply endorsement by

NIOSH. 

were used to monitor the carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), and 

oxygen. All data comparison is at 10 minutes after detonation. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

Several different types of explosive formulations were evaluated in air and argon 

atmospheres: ANFO (94/6), ANFO (92/8) , ANFO (94/6) with 5% added aluminum 

powder, an emulsion, an emulsion with 5 and 10% aluminum, a water gel, a gelatin 

dynamite, a semi-gelatin dynamite, and an ammonia gelatin dynamite. Some of these 

explosives were used to determine the overall fumes contribution associated with various 

types of commercial packaging. Packaging included Valeron*

 (high density polyethylene 

film), rigid paper tubes, waxed paper, and glass for some ANFO and emulsion blasting 

agents. 

RESULTS 

The gaseous products of explosive detonation depend upon the formulation and the 

conditions surrounding their use, but carbon dioxide, water vapor, and nitrogen are 

always produced. In addition, CO, NO, NO2, methane (CH4), and hydrogen (H2) may 

form in large or small quantities. All explosives generate CO and NO, with the CO 

production in some cases in amounts larger than that of NO4,5. Formulated commercial 

explosives usually generate between 6 to 31 liters of CO per kilogram (l/kg) of explosive 

(0.1 to 0.5 ft3

 per pound [lb]) in air.4,5 The oxygen balance of the explosive formulation 

(including the wrapper), generally controls CO and NO production. Excess fuel or 

negative oxygen balance generally results in increased CO production and decreased NO. 

On the other hand, less fuel or positive oxygen balance generally results in a decrease in 

CO and a significant increase in NO. When the NO contacts air, it oxidizes to NO2. NO2 

is approximately 10 times more toxic than NO and about 17 times more toxic than CO 

(30 CFR Part 15).6

 Also, NO, along with CO, can remain in the expanded rock for a long 

time and NO only gradually changes to NO2 with exposure to oxygen.7 NO2 will rapidly 

dissolve in water and adsorb strongly on most surfaces. 

Explosive formulations were detonated both in air and in argon, and the CO, NO, and 

NO2 were measured. Upon detonation, the generated turbulence rapidly mixes the 

combustion products within the sphere. This report only contains CO, NO, and NO2 data 

from the on-line instrumentation. At the time of writing, the GC results for H2, carbon 

dioxide (CO2), nitrous oxide (N2O), and hydrocarbons were not available, but will be 

reported later. 

Shown in Figure 2 is a typical concentration history of CO, NO, and NO2 products from 

the detonation of a 453.7-g (1-lb) charge of TNT flakes with a 74.0-g (0.163-lb) 50/50 

PETN/TNT booster in air. About 10 minutes after the detonation, the CO concentration 

reaches a maximum and stays relatively constant over the subsequent 50-minute 

recording period. On the other hand, the NO2 concentration increases as the NO oxidizes 

to NO2. During this sampling period, the oxygen concentration remains relatively 

constant at 18.1%. 

Illustrated in Figure 3 is a typical concentration history of CO, NO, and NO2 products 

from a 457.7-g (1-lb) charge of TNT flakes with a 73.8-g (0.163-lb) 50/50 PETN/TNT 

booster in argon (< 0.35 % O2). During the first 10 minutes after detonation, the CO 

concentration slowly rises from an initial concentration of about 7000 ppm to 7800 ppm, 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

where it remains nearly constant over the remaining 50-minute sampling period. Since 

there is little oxygen available to oxidize the NO to NO2, the NO concentration remains 

nearly constant over the sampling period. For this test in an argon-rich atmosphere, the 

NO2 concentration was negligible. This indicates that little NO2 was being produced in 

the detonation, but rather was produced during the post-detonation reaction in which NO 

was oxidized to NO2. Furthermore, the nearly 20-fold increase in CO concentrations in 

argon indicates that afterburning can play a large role in determining CO concentrations. 

Underground confinement will tend to minimize such afterburning and can lead to high 

CO concentrations (analogous to the argon results). 

A minimum of three trials was performed on each explosive formulation in each 

atmosphere with the average calculated on the samples taken 10 minutes after the 

detonation. The average and the +/- one standard deviation is shown as Y error bar on 

the graphs and tables. All comparisons were based on statistical analysis using a two way 

ANOVA with Bonferroni Multiple Comparison Test. 

NO-NO 2 Oxidation 

Elshout8 states that there are 3 reactions that result in the oxidation of NO to NO2. 

2NO + O2 · 2 NO2 (1) 

NO + O3 · NO2 + O2 (2) 

NO + RO2 · NO2 + RO (3) 

Elshout goes on to suggest that reaction (3) is only of importance in atmosphere 

containing high concentrations of reactive hydrocarbons in the presence of high UV 

radiation and reaction (2) will be important at lower NO concentrations in the presence of 

ozone. Based on Elshout’s analysis, reaction (1) will predominate under the conditions 

of this study,. The oxidation rate of NO to NO2 for the tests in air is consistent with those 

referenced and published by Baulch.9 For reaction (1), the rate conversion of NO to NO2 

is second order with respect to the NO concentration and first order with respect to the O2 

concentration, [(1⁄2d (NO)/dt = K * (NO)2

 * (O2)]. For NO concentrations less than 100 

ppm, the data reported here is consistent with reaction (1), yielding a rate constant of 

1.6E-38 cc/molecule-sec, in reasonable agreement with Baulch’s reported reaction rate 

constant of 2.01E-38 cc/molecule-sec. This analysis and agreement with Baulch’s work 

is based on the assumption that all NO converts to NO2 according to the above reaction, 

and little NO is lost to the wall of the sphere. The linear dependence of NO conversion 

with O2 explains why NO conversion is slow in an argon-rich atmosphere. Evaluation of 

explosive fumes production in an argon atmosphere may better represent the formation of 

fumes from explosive detonation in a low oxygen environment. Previous larger scale 

tests of fumes production involved detonation of explosives in air. Measuring fumes 

production in air, however, may not reliably characterize the actual toxic fumes 

production in field use, since it permits after-burning and oxidation of explosive products, 

which will not occur in a oxygen limited environment. 

Boosters 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

When using a blasting agent in trench blasting operations, a booster must be used for 

initiation. Even though the mass of booster may be a relatively small fraction of the mass 

of explosive, the contribution of the booster to the overall CO and NO toxic fume 

production may be significant and should be considered in blast design. Tests were 

conducted to measure the fumes production from commercial cast boosters (400-g, 0.9­

lb.). The commercial boosters were an average of 46% PETN and 42% TNT, with 12% 

aluminum, as identified by the manufacturer. The manufacturer lists a density range 

from 1.60 to 1.66 g/cc. Several commercial boosters were detonated in air and in argon, 

with and without wrapper, to quantify the production of CO and NO. Shown in Figure 4 

is the comparison of CO and NO production from the detonation of the commercial 

boosters (with wrapper) in air and in argon. As shown, there is more than a 34.5 fold 

increase in CO production when detonated in argon. The average CO production was 8.6 

(± 2.5) l/kg [0.14 (± 0.04) ft3

/lb)] in air compared to 298 (± 30) l/kg [4.76 (± 0.47) ft3/lb)] 

when detonated in argon without the secondary oxidation of CO to CO2. Also shown is 

the average fumes production from a NIOSH/PRL cast 50/50 booster in air and in argon 

without a paper wrapper. When detonated in air the CO averaged 10.48 (± 0.92) L/kg 

[0.17 (± 0.01) ft3

/lb)] and in argon about a factor of 23 higher at 241 (± 14) L/kg [3.85 (± 

0.23) ft3

/lb)]. 

TNT 

Pelletized TNT is one of the explosives associated with two CO poisoning incidents. To 

quantify the CO and NO produced from the detonation of TNT charges, both cast and 

flaked TNT charges were studied. A cast 5-cm (2-in.) diameter by 12.7 cm (5-in.) long 

charge, and flaked TNT loaded into a 5 cm (2-in) diameter by 70-cm (24-in) long glass 

tube, were both initiated with a 50/50 Pentolite cast booster. Figure 4 compares the CO 

and NO produced from the detonation of flaked TNT in air and in argon. In argon, an 

average of 393.2 (± 6.4) L/kg [6.29 (± 1.10) ft3

/lb)] of CO and 5.57 (± 0.10) L/kg [0.09 (± 

0.002) ft3/lb)] of NO were produced. When detonated in air, most of the 393 L/kg was 

oxidized to CO2, while the NO production was about the same in air as in argon. The CO 

produced from the TNT flake (bulk loading density 0.89 g/cm3) was about 1.79 times 

higher than that produced from cast TNT (density1.58 g/cm3). This CO production from 

the detonation of TNT is consistent with results reported by Schmidt10 who describes the 

decomposition of TNT for the density loadings of 1 and 1.59 g/cm3. Schmidt predicts 

that about 1.8 times more CO is produced at 1 g/cm3

 than at 1.59 g/cm3 due to the less 

ideal detonation properties of the lower density material. 

ANFO 

Common ANFO blends were included in this study since they have been associated with 

CO migration and poisoning incidents in the past,. The pulverized (< 250 microns) 

ammonium nitrate was mixed with #2 diesel fuel oil and the mixture was packed into a 5­

cm (2-in.) OD glass tube closed at one end with the 70-gram booster. The mixtures used 

were 94/6 ANFO, 92/8 ANFO, and 94/6 ANFO with 5% added aluminum. The bulk 

non-tamped loading density of the pulverized ANFO (< 250 microns) averaged 0.82 g/cc. 

The average velocity of detonation (VOD) was 3,920 (± 670) m/s [12,860 (± 2,180) ft/s)]. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

Figure 5 compares the CO and NO produced from the detonation in argon of ammonium 

nitrate with 6 and 8% diesel fuel and 94/6 ANFO with 5% added aluminum. ANFO 

(94/6) produces an average CO of 13.8 (± 4.5) L/kg [0.22 (± 0.07) ft3

/lb)] and 25.5 (± 

5.1) L/kg [0.41 (± 0.08) ft3

/lb)] of NO. As expected, by increasing the fuel oil to 8%, the 

CO production increased 2.5 times to 35.1 (± 6.4) L/kg [0.56 (± 0.10) ft3/lb)], with a 

corresponding 14% reduction in NO to 22.0 (± 5.1) L/kg [0.35 (± 0.08) ft3/lb)]. Adding 

5% aluminum powder to the 94/6 ANFO mix slightly increases the CO production to 

25.3 (± 6.9) L/kg [0.40 (± 0.11) ft3

/lb)] while slightly decreasing the NO to 16.2 (± 5.5) 

L/kg [0.26 (± 0.09) ft3

/lb)]. 

Emulsions 

Emulsion A 

Emulsion A, a bulk emulsion blasting agent, has been formulated to reduce the 

production of NO2. It is mostly used in the large cast blasts and was tested in this study 

for comparison with cap-sensitive emulsions. Emulsion A has a critical diameter of < 

3/4-inch (steel pipe) and is not cap sensitive (No. 8 cap).11 The bulk emulsion was placed 

in a 2-in. OD glass tube and initiated with a 70-gram 50/50 PETN/TNT booster. The 

density of the emulsion was 1.18 g/cc. The VODs averaged 4,735 m/s (15,530 ft/s) in a 2 

in. diameter glass tube. The manufacturer published value is 5,790 m/s (19,000 ft/s) shot 

in a 6.75 in. borehole. 

Emulsion B Series 

Emulsion B series is an emulsion commercially produced with 0%, 5%, and 10% added 

aluminum (Al) in two different packaging materials. One material was Valeron plastic 

film and the other was a rigid cardboard tube. The densities ranged from 1.17 g/cc to 

1.19 g/cc, increasing in density with aluminum addition. The VODs ranged from 4,791 

m/s (15,714 ft/s) to 5,260 m/s (17,250 ft/s) when initiated with a #8 detonator, which 

agreed with the manufacturer published values of 4,724 m/s to 5,182 m/s (15,500 ft/s to 

17,000 ft/s). The packaged charge size ranged from 1-1/4-in. OD by 12-in. length to 2-in. 

OD by 16-in. length. The emulsion B series is listed as IME fume class 1 (less than 0.16 

cu. ft. poisonous gases produced per 1-1/4-in. x 8-in. cartridge of explosive)4 without 

aluminum addition and IME fume class 2 (0.16 - 0.33 cu. ft. poisonous gases produced 

per 1-1/4-in. x 8 in. cartridge of explosive)4

 with aluminum addition. 

Figure 6 compares the CO and NO produced in argon by the detonation of the Emulsion 

A in glass and Emulsion B-0 (0% Al) in both poly and cardboard wrapper, along with the 

average measured VOD for each. The average CO and NO production expected from the 

50/50 booster in argon was subtracted from that of Emulsion A blasting agent. All other 

emulsions were #8 cap-sensitive. Results show that the CO and NO were lowest for the 

Emulsion A blasting agent. The Emulsion B-0 cardboard wrapper weighs 83.5 grams for 

a 2-in. by 16-in. cartridge and the poly wrapper weighs 27.3 grams for a 1-1/4-in. by 12­

in. cartridge. Emulsion B series emulsions are provided either in poly wrapper or in a 

cardboard wrapper with no adjustment in oxygen balance. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

In Figure 7, the CO produced by the detonation of Emulsion B-0 and Emulsion B-10 

(10% Al) in the cardboard wrapper is over twice that produced when shot in the poly 

wrapper. The NO shows a 40% reduction from 15.7 (± 0.3) l/kg [0.25 (± 0.004) ft3

/lb)] 

to 9.3 (± 0.3) l/kg [0.15 (± 0.004) ft3/lb)] for Emulsion B-0, whereas Emulsion B-10 

dropped 25% from 10.5 (± 0.2) l/kg [0.0.17 (± 0.002) ft3

/lb)] to 7.9 (± 0.6) l/kg [0.13 (± 

0.009) ft3/lb)]. 

Figure 7 shows the CO and NO produced from Emulsion B-0, Emulsion B-5 (5% Al), 

and Emulsion B-10 detonated in argon with their cardboard wrappers. Results do not 

indicate a significant difference in CO production with the 10% aluminum, but there is a 

reduction of 15% in NO from 9.29 (± 0.28) l/kg [0.15 (± 0.005) ft3/lb)] to 7.92 (± 0.58) 

l/kg [0.13 (± 0.009) ft3/lb)]. The CO production is about the same for Emulsion B-0-poly 

and Emulsion B-10-poly, while there is a corresponding 33% decrease in NO production 

with 10% added aluminum from 15.7 (± 0.3) l/kg [0.25 (± 0.004) ft3

/lb)] to 10.5 (± 0.2) 

l/kg [0.17 (± 0.003) ft3

/lb)]. Generally, with an increase in aluminum in Emulsion B, 

there is no significant difference in CO production but the NO decreases. The packaging 

of the explosives can play a key role in the production of CO and NO. The manufacturer 

should include the contributions of the final packaging to oxygen balance the explosive. 

Also, the blaster must understand the product is oxygen balanced and must be used only 

in the way recommended by the manufacturer. Blasters should not use additional 

borehole liners unless specified by the manufacturer or understand the consequences of 

doing otherwise. 

Watergel 

Watergel A 

Watergel A is an explosive designed for trenching operations and hole depths of less than 

20 ft. Watergel A is packaged in a poly wrapper with a density of 1.18 g/cc. The 

cartridge dimension tested was 2 inches in diameter by 16 inches long and weighed 13.5 

g. The VODs recorded during testing averaged 3,991 (± 221) [13,090 (± 725) ft/s)] 

unconfined, which is lower than the manufacturer’s reported VOD of 5,091 m/s (16,700 

ft/s) confined. 

The CO and NO detonation products from Watergel A are shown in Figure 6. The 

average CO produced by Watergel A, 22.9 (± 1.8) l/kg [0.37 (± 0.03) ft3

/lb)], is 1.8 times 

higher than the Emulsion B-0 emulsion in poly. The NO is 24% lower for the Watergel 

A, 11.9 (± 0.6) l/kg [0.19 (± 0.01) ft3

/lb)], than for the Emulsion B-0 in poly. 

Dynamites 

A few of the CO poisoning incidents involved the use of dynamites, which were therefore 

considered as part of this study to quantify the relative production of CO and NO from 

selected dynamites used for trenching operations. 

Gelatin dynamite 

Generally, gelatin dynamites are cap sensitive and nitroglycerine based. Some use 

nitrocotton rather than absorbent dopes to hold the nitroglycerine and help maintain 

product consistency for use in water-resistant applications.12 Dynamite A was imported 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

from Europe and distributed in North America and donated for this study. The density of 

Dynamite A was 1.48 g/cc and was received in 2-in. diameter by 16-in. long cartridges. 

Dynamite A was supplied in a heavy wax paper wrapper with a stiff outer cardboard tube. 

The manufacturer reports a VOD of 6,400 m/s (20,992 ft/s) unconfined. In NIOSH/PRL 

testing, the VOD averaged 2,312 (± 239) m/s [7,583 (± 2,378) ft/s)], unconfined. When a 

50/50 pentolite booster initiated a charge, the VOD averaged 6,136 m/s (20,126 ft/s). 

This is expected and agrees with previous publications citing two characteristic VODs for 

gelatin dynamites.13, 14 

Semi-Gelatin dynamite 

Cap-sensitive semi-gelatin dynamites are ammonia dynamites containing a small portion 

of nitrocotton as a gelling agent and deriving most of their energy from the reaction of 

ammonium nitrate and sodium nitrate with fuel.12 Dynamite B has a density of 1.30 g/cc 

and reported good water resistance. The 1-1⁄2 in. OD by 16-in. long charges arrived 

packaged in wax paper. Dynamite B is characterized by the manufacturer as an IME 

fume class 1 with a reported VOD of 4,300 m/s (14,104 ft/s). The average measured 

VOD was 4,253 m/s (13,950 ft/s). 

Ammonia gelatin dynamite 

Ammonia gelatin dynamites derive part of their strength from ammonium nitrate12. 

Dynamite C has a density of 1.43 g/cc and has a reported excellent water resistance. The 

1-1⁄2-in. OD by 8-in. long cartridges are packaged in 12.6 grams of wax paper. Dynamite 

C is listed as IME fume class 1 and has a reported unconfined VOD of 6,000 m/s (19,680 

ft/s). Experimental VOD averaged 2,644 m/s (± 288 m/s) [8,672 (± 946) ft/s)]. Although 

not specified by the manufacturer, initiation with a 70 g 50/50 pentolite booster in 2 in. 

diameter glass more than doubled the VOD with an average of 5530 m/s (18,133 ft/s). 

Carbon monoxide and nitric oxide production from the three dynamites, as received, are 

shown in Figure 8. Of the three dynamites evaluated, Dynamite A (without the cardboard 

tube) produced the largest quantity of CO, {52.1 (± 2.0) l/kg [0.83 (± 0.03) ft3

/lb)]}, and 

NO, {60.7 (± 5.4) l/kg [0.97 (± 0.09) ft3/lb)]}. Dynamite C produced the least CO, {18.0 

(± 1.3) l/kg [0.29 (± 0.02) ft3

/lb)]}, and the least NO, {31.1 (± 3.2) l/kg [0.50 (± 0.05) 

ft3/lb)]}. Dynamite B, with the much higher VOD, fell between Dynamite C and 

Dynamite A with a CO production of 25.3 (± 2.7) l/kg [0.40 (± 0.04) ft3

/lb)] L/kg and NO 

of 34.1 (± 2.5) l/kg [0.54 (± 0.04) ft3/lb)]. One might expect that with higher VODs, 

higher reaction temperatures, and more efficient combustion, less CO and NO would be 

formed. However, results show that Dynamite C produces about the same NO and about 

29% less CO than Dynamite B. 

Toxic Fume Comparison 

IME 

Institute of Makers of Explosives (IME) Fume classification standard for Class 1, 2, and 

3 requires that CO and hydrogen sulfide (H2S), produced by an explosive or blasting 

agent fall within one of the three ranges. IME Fumes Class 1 requires less than 0.16 ft3 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

per 1-1/4-in. diameter by 8-in. cartridge, Fumes class 2 requires 0.16 to 0.33 ft

3

, and 

Fumes Class 3 requires 0.33 to 0.67 ft3. As of the writing of this paper, the IME Fume 

Classification, by definition, is based on tests conducted in the Bichel Gauge12. 

The IME Fumes Classification and the VODs as reported by the manufacturer are 

presented in Table 1. For comparison purposes only, the IME Fume Class based only on 

the measured CO in argon (no H2S) from this study is also presented. Results would 

indicate Dynamite C, Emulsion B-0 poly, Emulsion B-5 cardboard, and the Emulsion B10 in cardboard agreed in IME fume classification between the manufacturer and those 

based on current sphere tests. Dynamite B and Emulsion B-0 cardboard under these test 

conditions produced more CO than expected and thus would be classified as Class 2 

instead of the reported Fumes Class 1. Dynamite A, on the other hand, shows the largest 

difference between the manufacturer’s reported IME class 1 and the current sphere test as 

a Class 3. Also, the measured VOD (without booster initiation) from Dynamite C and 

Dynamite A were both significantly lower than the manufacturer’s reported values. 

However, the fumes production from Dynamite C was much lower than those from 

Dynamite A and many other explosives. 

Federal Relative Toxicity Standard (30 CFR part 15) 

Federal regulatory standard 30 CFR part 156

 provides the approval requirement for toxic 

gas production from permissible explosives for use in underground coal and other gassy 

mines. The 30 CFR standard requires that the total poisonous gases do not exceed 155 

cm3

/g ( 2.5 ft3/lb) at standard conditions. The total toxic gas weighting factors are based 

on TLVs, Threshold Limit Values, published in the 1988-89 ACGIH (American 

Conference of Governmental Industrial Hygienists) T.L.V.s. Using CO as a reference 

gas with unit relative toxicity, CO2 is rated as 0.01, NO is 2, NO2 is 17, ammonia (NH3) 

is 2, H2S is 5, and sulfur dioxide (SO2) is 25. Carbon dioxide is regarded as a toxic gas 

because it is produced in high concentrations and is more dense than air. It can displace 

oxygen and cause suffocation, particularly in lower mine areas and poorly ventilated 

spaces. In this paper, the primary toxic gases considered are CO, NO, and NO2. Once 

the NO mixes with oxygen, the NO oxidizes to NO2, which is about 8.5 times more toxic. 

Even though the explosives tested in this study are not permissible explosives for use in 

underground coal or other gassy mines, the relative toxicity scale defined in 30 CFR Part 

15 was used to compare them. Shown in Table 2 is the summary of the average fumes 

along with the calculated relative toxicity based only on CO, NO, and NO2 production for 

detonations in argon. Using explosives that produce less toxic gases should help reduce 

the amount of entrapped toxic gases that can migrate into confined spaces, and less toxic 

gases that require post-shot mitigation. The use of explosives that produce less CO and 

NO does not ensure that these gases will not enter nearby dwellings. But by reducing 

their overall concentration in the stable detonation products, conceptually, the 

concentration of the gases that might enter a nearby dwelling should be reduced. 

Of the explosives tested, Emulsion A blasting agent produced the lowest relative toxicity 

while flaked TNT was the highest. Also noteworthy is the change in distribution of CO 

to NO with the change in wrapper material. Even though the relative toxicity remains 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

about the same for both, the cardboard wrapper produces more CO than NO, while the 

trend is reversed for the poly wrapper. The ranking shown in Table 2 serves to illustrate 

that from a fumes standpoint only, some explosives used in trenching operations may be 

a better choice than others when blasting under heavy containment and close to occupied 

dwellings. 

Generally, results of this study show that the CO production from the detonation of 

explosives depends on the type of wrapper. Poly or Valeron wrappers generally produce 

less CO and more NO than cardboard since they provide less of a fuel contribution. 

Adding aluminum to Emulsion B in a poly wrapper or cardboard wrapper did not 

significantly change the CO production but the NO decreased. 

TNT stood out as the most significant producer of CO at 393 L/Kg. Explosives and 

wrappers should be considered as part of the overall blast design especially when blasting 

near occupied dwellings and where immediate shot mucking is not possible. Also, fuelrich boosters containing mixtures of PETN/TNT (Pentolite) used for initiating blasting 

agents may be a significant contributor to the total CO trapped in the expanded ground. 

Under these test conditions, the results in Table 2 would indicate that detonation products 

produced from 1 kg of the commercial booster (298 L/kg) with wrapper would produce 

about the same CO as 32 kg (298 L/9.3 L/kg) of Emulsion A (9.3 L/kg). 

Some of the fume classifications and VODs reported in this study differed from those 

reported by the manufacturer. Dynamite A and Dynamite C VODs differed significantly 

when initiated with a #8 cap and with a 70 g booster. Although the explosive is reported 

#8 cap sensitive, the VOD greatly differs with the mode of initiation. Under these test 

conditions, some explosives would be classified differently than they are in the IME 

classification scheme. Several manufacturers report an IME classification based on a 

thermodynamic chemical equilibrium calculations rather than on Bichel Gauge test 

results. Additional studies are underway at PRL to compare Bichel Gauge tests with 

reported values and those based on this new methodology. 

SUMMARY 

Preliminary results indicate that this test method for comparing the relative toxic fumes 

production from commercial explosives shows promise for providing a performance 

based methodology that may help in the overall blast design when blasting near occupied 

dwellings. 

Blasters’ awareness is important in preventing future CO poisonings. Among the many 

factors considered for trench blasting near occupied dwellings, toxic fumes production 

should also be accounted when selecting explosives and primers. 

Whenever possible, the shot material should be carefully excavated as soon as possible 

after detonation. Alternately, surface material could be excavated before detonation and 

blast mats used during blasting where appropriate. Although not readily apparent, 

blasters should be vigilant about looking for possible pathways from the blast site to 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

nearby underground enclosed spaces. Finally, nearby enclosed spaces should be 

monitored for toxic gases before and after blasting. 

ACKNOWLEDGMENTS 

The work of Cindy Hollerich and Paul Kolarosky, Physical Science Technicians, who 

instrumented and conducted the 12-ft (3.7-m) sphere fume studies at NIOSH/PRL, is 

gratefully acknowledged. Without their help, this lengthy study could not have been 

completed in a timely manner. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 14 o

Table 1 - IME Fume Classification Comparison. 

Explosive IME 

Classa Reported VODa Densitya IME Classb Measured VODc 

Dynamite A 1 6,400 m/s (20,992 ft/s) 1.48 g/cc 3 2,343 m/s (7,685 ft/s) 

Dynamite C 1 6,000 m/s (19,680 ft/s) 1.43 g/cc 1 2,601 m/s (8,531 ft/s) 

Dynamite B 1 4,300 m/s (14,104 ft/s) 1.30 g/cc 2 4,253 m/s (13,950 ft/s) 

Emulsion B-0 poly 1 5,183 m/s (17,000 ft/s) 1.17 g/cc 1 5,152 m/s (16,899 ft/s) 

Emulsion B-0 cdbd 1 5,183 m/s (17,000 ft/s) 1.17 g/cc 2 5,111 m/s (16,764 ft/s) 

Emulsion B-5 cdbd 2 5,030 m/s (16,500 ft/s) 1.17 g/cc 2 4,766 m/s (15,632 ft/s) 

Emulsion B-10 poly 2 4,726 m/s (15,500 ft/s) 1.19 g/cc 1 4,773 m/s (15,655 ft/s) 

Emulsion B-10 cdbd 2 4,726 m/s (15,500 ft/s) 1.19 g/cc 2 4,937 m/s (16,193 ft/s) 

a

 Data reported by manufacturer. 

b

 IMEClassificationbased on this study using CO only. c

 VOD measured in this study. 

Table 2 - Toxic Fumes Production and Relative Toxicity per 30 CFR part 15. 

Explosive COa, e, f NOb, e, f c, e, f NO2 Toxic Fumesd, e 

Emulsion A 9.3 (3.5) 7.4 (0.9) 0 (0) 24.0 

Emulsion B-10 poly 13.6 (0.5) 10.5 (0.2) 0 (0) 35.0 

Emulsion B-0 poly 12.9 (1.3) 15.7 (0.3) 0.1 (0.1) 45.9 

Emulsion B-5 cdbd 27.6 (1.8) 9.4 (0.3) 0 (0) 46.4 

Emulsion B-10 cdbd 31.9 (1.3) 7.9 (0.6) 0 (0) 47.9 

Emulsion B-0 cdbd 29.4 (3.8) 9.3 (0.3) 0 (0) 48.0 

Watergel A 22.9 (1.8) 11.9 (0.6) 0.1 (0.1) 48.9 

94/6 ANFO 5% Al 25.3 (6.9) 16.2 (5.5) 0.6 (0.8) 68.0 

94/6 ANFO 13.8 (4.5) 25.5 (5.1) 0.4 (0.5) 72.3 

92/8 ANFO 35.1 (6.4) 22.0 (5.1) 0.1 (0.1) 80.5 

Dynamite C 18.0 (1.3) 31.1 (3.2) 2.0 (0.4) 114.0 

Dynamite B 25.3 (2.7) 34.1 (2.5) 3.9 (0.8) 159.9 

Dynamite A w/ tube 51.8 (2.9) 50.6 (1.9) 3.3 (0.9) 208.5 

TNT cast 219.2 (11.5) 2.4 (0.9) 0 (0) 224.0 

Dynamite A w/o tube 52.1 (2.0) 60.7 (5.4) 3.3 (1.7) 230.2 

50/50 PETN/TNT 240.6 (14.2) 2.2 (0.4) 0 (0) 245.0 

Commercial booster w/o wrapper 250.8 (22.4) 1.3 (1.3) 0 (0) 253.3 

Commercial booster w/ wrapper 297.8 (29.6) 0.8 (0.1) 0 (0) 299.3 

TNT flakes 393.2 (6.4) 5.6 (0.1) 0 (0) 404.3 

a, b, c CO, NO, and NO2 measured in an argon atmosphere, l/kg (ft3

/lb). 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

d

 Toxic fumes, l/kg (ft3/lb), calculated per 30 CFR Part 15.20 (g)(1) and (2). Only 

includes the CO, NO, and NO2 that were measured. All other gases are excluded.
 e

 ft3/lb = (0.016) x l/kg

f

 One standard deviation.
 
Figure 1 - NIOSH/PRL 12-ft. diameter sphere. Figure 2 - On-line results of flake TNT (453.7 g)

with 50/50 PETN/TNT booster (74.0 g) shot in an 

air atmosphere. 

Figure 3 - On-line results of flake TNT (457.7 g) 

with 50/50 PETN/TNT booster (73.8 g) shot in an 

argon-rich, oxygen-deficient atmosphere. 

Figure 4 - Fumes results for commercial booster 

(with and without paper wrappers), flake TNT, 

and cast TNT shot in an argon-rich, oxygendeficient atmosphere. 

Figure 5 - Fumes results for 94/6 ANFO, 92/8 

ANFO, and 94/6 ANFO with 5% aluminum 

addition shot in an argon-rich, oxygen deficient 

atmosphere. 

Figure 6 - Fumes results for Emulsion B-0 (with 

poly and cardboard wrappers), Watergel A, and 

Emulsion A shot in an argon-rich, oxygendeficient atmosphere. 
Copyright © 2003 International Society of Explosives Engineers

2003G Volume 2 - Toxic Fume Comparison of a Few Explosives Used in Trench Blasting 

Figure 7 - Fumes results for Emulsion B-0 (in poly 

and cardboard wrappers), Emulsion B-5 (in 

cardboard wrappers), and Emulsion B-10 (in poly 

and cardboard wrappers) shot in an argon-rich, 

oxygen-deficient atmosphere. 

Figure 8 - Fumes results for Dynamite C 

(ammonia gelatin dynamite), Dynamite B (semigelatin dynamite), and Dynamite A (gelatin 

dynamite, with and without cardboard tubes) sho

in an argon-rich, oxygen-deficient atmosphere. 

REFERENCES 

(1)	 Santis, Lon D., A Summary of Subsurface Carbon Monoxide Migration Incidents. 

Proceedings of the Twenty-Seventh Annual Conference on Explosives and Blasting 

Technique. International Society of Explosives Engineers, 2001 volume 2-AS, pp. 

143-154, 2001. 

(2)	 Mantel, R., L. Trépanier, L. Boutin, M. Lavigne, B. Lévesque, G. Sanfaçon, P. 

Auger, L. Galarneau, and P. Brousseau. Carbon Monoxide Poisoning From 

Blasting Operations in Construction Works, An Earth Odyssey, 2001. 

(3)	 Santis, L. C. and R. A. Cortese, A Method of Measuring Continuous Detonation 

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Conference on Explosives and Blasting Technique. Orlando, FL, February 4-8, 

1996. 

(4)	 Santis, L., J. Rowland, D. Viscusi, and M. Weslowski, “The Large Chamber Test 

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(5)	 Persson, P., R. Holmberg, and J. Lee. Rock Blasting and Explosives Engineering, 

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(9)	 Baulch, D.L.; D.D. Drysdale; and D.G. Horne. Evaluated Kinetic Data for high 

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(10) Urbanski, T. “Chemistry and Technology of Explosives,” Volume 1, pp. 318, 1964. 

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