Fugitive Carbon Based Gases 

Blasting Related or Not 

Kenneth K. Eltschlager
 

Mining Engineer 

Office of Surface Mining Reclamation and Enforcement 

Pittsburgh, PA 

Marcia Harris 

Chemical Engineer 

National Institute for Occupational Safety and Health 

Pittsburgh, PA 

Fred Baldassare 

Hydrogeologist 

Pennsylvania Department of Environmental Protection 

Pittsburgh, PA 

Abstract 

Surface mine blasting was recently investigated as a potential source of high concentrations of 

stray gases found in nearby residences of western Pennsylvania. In one incident carbon 

monoxide was detected in a home and in the other, high concentrations of carbon dioxide were 

found in a home. Both carbon monoxide and carbon dioxide are by-products of blasting. 

However, other potential sources of these gases may also exist in a residential setting. In each 

case, gas chromatography (GC) and carbon isotopic analyses were used to define atmospheric 

concentrations inside the homes, and to determine the source of a stray gas. Molecular and 

isotopic analyses provide geochemical evidence as to the origin and source of the stray gas. This 

paper discusses elements of a stray gas investigation and the analyses necessary to identify the 

source of a stray gas. 
Introduction 

Elevated concentrations of various gases have long been known to be dangerous to underground 

miners. Prior to active mine ventilation, stagnant mine atmospheres allowed gases to 

accumulate, sometimes to lethal levels. Common terms were associated with their detrimental 

effect and continue to be used today. Black damp is caused by an oxygen deficient atmosphere 

and is often a result of carbon dioxide (CO2) displacing oxygen. White damp is caused by 

elevated levels of carbon monoxide (CO). Fire damp refers to explosive levels of methane 

(CH4). As a result of research and advances in mining law, most of the gas sources are currently 

identified and either eliminated or diluted with active ventilation. Today all active mines are 

required to provide active ventilation to vent unwanted gases. 

One of the identified potential sources of black damp and white damp in underground mines is 

blasting. To minimize the volume of adverse gases generated by blasting, permissible explosives 

were developed for application in underground coal mines. This was done as an effort to protect 

miners from overexposure to toxic gases. With the addition of active mine ventilation, most, if 

not all, of the black damp and white damp in the underground miner’s workplace have been 

eliminated. 

Other explosives continue to be used at surface mines and quarries. Contrary to underground 

mining applications, surface blasts occur in the open atmosphere and any fumes are quickly 

dissipated into the atmosphere. However, as blasting nears a residential area, in both construction 

and mining, the designs become more confined in order to prevent flyrock. As the blasts become 

more confined, the gases are trapped in the ground. If venting to the atmosphere is not allowed, 

the gases will follow the path of least resistance. Occasionally, the gases will migrate into 

nearby residences and cause the occupants to become ill. 

Since 1988, at least eleven incidents of stray CO migration from blasting sites have been 

documented1,2,3. In a separate instance, elevated levels of CO2 were alleged to have been caused 

by blasting4. Although both gases are generated in the blasting process, is blasting the source of 

the stray gases causing a problem? 

Gas Properties 

The physical and chemical properties of gases allow their movement to be predicted and their 

reactions in the atmosphere to be determined5. Gases migrate from high to low pressure areas 

and from high to low concentrations by molecular diffusion. Molecular diffusion becomes a 

prominent factor when flow rates are very low or stagnant. Blasting gases when confined in the 

ground are under pressure and will migrate to a lower pressure area through the path of least 

resistance. Once the pressure has equalized, the gases in the ground will dissipate through 

molecular diffusion or in response to changes in barometric pressure. Residual gases in the 

ground could last for years. The physical properties of CO and CO2 are a factor in how they may 

migrate and are important considerations in sampling. 

CO is a colorless, odorless, and tasteless gas with a specific gravity of 0.97 (compared to air). Its 

presence is due to incomplete oxidation or combustion of carbon. Very few natural CO sources 

exist. The most common source is automobile exhaust. Appliances, including gas cook tops, 

gas heaters, furnaces, and wood stoves can also contribute CO. Inadequate maintenance, broken 
 

 

parts, or back drafting due to the design and construction of a house can make these devices 

dangerous. CO binds strongly with hemoglobin (carrier of oxygen from the lungs to the organs) 

in the blood. The CO-hemoglobin bond is 200 times stronger than O2-hemoglobin. It is not 

easily respired out of the human body. Thus the blood cannot carry enough O2 to sustain bodily 

functions. 

Carbon dioxide is odorless, colorless, and tasteless and has a specific gravity of 1.53. It is a 

basic by-product of respiration and combustion. With a specific gravity heavier than air, the gas 

will stratify in a non-ventilated, confined area with highest concentrations at the base of a 

structure. CO2 is not toxic to humans but in elevated concentrations, it can displace O2 and result 

in asphyxiation (lack of oxygen). 

Source of Carbon Based Gases from Blasting 

All explosives create an amount of CO and CO2. Depending on the oxygen balance of the 

formulation, some explosives produce more CO than others. The commonly used explosives 

contain an organic carbon. For simplicity, ammonium nitrate and fuel oil (ANFO) will be given 

as an example. 

The byproducts of the detonation of ANFO are primarily water (H2O), nitrogen (N2) and carbon 

dioxide (CO2), all nontoxic to people. In an ideal reaction1: 

3NH4NO3 + CH2 => 7H20 + CO2 + 3N2 

Noxious fumes are generated when the fuel oil portion is incorrect, water is introduced into the 

ANFO, or optimum detonation velocities are not attained due to inadequate priming. Generally, 

whenever the reaction becomes less efficient, toxic gases (fumes or Asmoke@) are produced. 

These secondary byproducts are CO and nitrogen oxides (NOx). 

The source of carbon in both CO and CO2 is the fuel oil (CH2). It is thermogenic in origin, 

derived from an organic source that was formed millions of years ago. This will play an 

important role when trying to determine the source as discussed later in this paper. 

Migration Pathways 

The migrations pathways may be in multiple directions from a blast. Gases can travel through 

rock pores and fractures5. The porosity and permeability of the transmitting medium affect the 

travel rates. Generally, pressure gradients cause gases to migrate to areas of lower pressure. 

Sometimes, gases will follow man made features such as buried pipelines and other utilities. 

Fractures provide a significant migration pathway. They include natural breaks produced by 

jointing and stress relief. The fractures are avenues for gases to move from one area or level to 

another through differing rock units. Faulting may also produce a conduit for gases to travel 

from its source. Conversely, faults can form a barrier against movement when permeable units 

on one side of the fault are in contact with less permeable units on the other side. 
Gas Sampling and Thresholds 

Gases can become dangerous in confined areas where ventilation is minimal. As the gases move 

through the ground and enter a residence, they will generally accumulate in the lower or below 

ground portions of a building. ALWAYS TEST THE ATMOSPHERE FOR GASES BEFORE 

ENTERING A CONFINED AREA! A confined area may be a basement, crawl space, closet, 

well house, manhole, trench, etc. Remember, CO2 can stratify because it is more dense than air. 

Entry testing should include oxygen, CO2, CO, and CH4 (explosive at 5 %). If there are 

dangerously elevated levels of CO2, the oxygen reading will be low and alarm. 

NIOSH6,7 recommends that work areas not exceed a time weighted average of more than 35 ppm 

CO and 0.5 % (5000 ppm) CO2 over an 8-hour period. For residential structures, EPA 

recommends no more than 9 ppm over an 8-hour period for CO. NIOSH also recommends a 

short term exposure limit (< 15 minutes) of 3 % CO2 and a maximum limit of 200 ppm for CO. 

Testing with Field Meters 

Portable multi-gas monitors used for confined space work can be outfitted with data loggers. 

These units can be left on for extended periods of time, powered by household current, to 

monitor a project site. Their portability and ease of use make them ideal for field work. A 

multi-gas monitor for blasting investigations should include CO2, CO, O2, and CH4. 

The monitors should alarm when conditions for imminent danger exist. Because of constant 

changes in atmospheric conditions, a data logger on a continuous monitor is an important 

investigative tool. The data logger can improve the quality of the field data and reduce the 

amount of time required to obtain samples. Data recorded over a known period can be correlated 

with other conditions that may change at the test site. Gas concentrations may vary with changes 

in temperature and/or barometric pressure. 

Generally, the gas measurement equipment used depends on the accuracy required and resources 

available to the field personnel. The most common field measurements of carbon gases are 

obtained from portable meters equipped with sampling wands and pumps. Figure 1 displays a 

portable meter used to sample gases. In addition to spot checking gas levels, many of the meters 

on the market today are capable of continuously recording gas measurements. 

In homes, a low level of any gas in a confined area is usually a sign of a concentrated point 

source of entry or generation in a building5

. Confined spaces must be carefully sampled to 

prevent normal air from diluting gases in the area to be sampled. Sampling should be performed 

through an existing opening or slightly opened door. Remember CO will evenly diffuse 

throughout the room and CO2 will settle to the floor. Once safely inside, the uphill edges of 

slabs or paved areas should be evaluated to determine if gas is exiting to the atmosphere. Test all 

cracks, joints, floor drains, pipe entrances, or other openings in the ground or in the basement of 

the structure. Beyond the obvious sources, all potential entry points, traps, and potential sources 

of combustion in structures must be tested. Gases most often enter structures through a 

basement. 

Construction trenches and subterranean structures such as tanks, vaults, and drain fields may be 

sources or conduits. These features should be checked for the presence of gas and evaluated as 
potential sources. Care should be taken to preserve the atmosphere of these confined spaces. 

For example, the gas concentration may be greatly diluted or lost if a manhole cover is opened to 

test for gas. In this case, it is preferable to sample through a hole in the manhole cover. 

Figure 1. Drager MultiWarn II .

Boreholes between the blast and problem areas should also be installed and tested to attempt to 

identify pathways (Figure 2).

Figure 2. Borehole monitoring with sampling wand.

 Portable meters with pumps and sampling wands can reach a depth 

of approximately 6 feet in the hole. If sampling is required at the bottom of a hole, tubing can be 

lowered to the bottom. Boreholes are best sampled on days when barometric pressures are 

dropping and gases may be exiting the ground. 

Field measurements are necessary to identify point sources and gas response to atmospheric 

conditions but are not as accurate as laboratory analyses. If the source is to be identified, grab 

samples are required. 

Grab Samples 

Grab samples of the gases should be obtained for molecular analyses in the laboratory. Gas 

samples for laboratory analysis can be collected in a variety of commercially available 

containers, including glass sampling bulbs, sampling bags, vacutainers, and various glass bottles. 

Grab samples should be obtained at the entry points identified during field testing of the site 

(Figure 3). If a room is unsafe to enter, the sample should be taken from the atmosphere. 

Sample wands with an aspirator or pump are necessary to take point source samples (Figure 4). 

Small hand pumps can be used to collect a sample. Gas samples should be collected in Tedlar® 

bags, vacuum tubes, or other impermeable environmental sample bags. Gas analyses in the 

laboratory are generally conducted by gas chromatography. 

Detector tubes will provide only field quality sample results and are not recommended for 

detailed investigations where quantitative data are required. Detector tubes must be selected for 

each particular gas to be tested, often requiring trial and error sampling. 
Figure 3. Rock ledge entry points. Figure 4. Aspirator pump and Tedlar bag .

Laboratory Analysis 

Molecular analysis provides quantitative analysis of a grab sample. Molecular analyses are 

fundamental to attempt to identify the source of gases. Results for molecular analyses combined 

with other aspects of a site specific investigation may be sufficient to interpret the source of the 

gases. Molecular analysis for blasting investigations should include N2, O2, CO2, CO, CH4, H2, 

and Ar. 

Due to other environmental processes in the subsurface, molecular analyses alone may not 

always be sufficient to interpret the source of gas. Fluctuating barometric conditions, chemical 

fractionation, and bacterial oxidation may alter the composition of a gas as it migrates from the 

source area. 

Additionally, in areas where several potential sources may occur, it is advisable to conduct 

analysis for carbon and hydrogen isotopes. Isotopes are different forms of the same element. 

For example, the origin and source of stray CH4 can be determined through isotopic analysis of 

carbon (12C, 13C, and 14C), and hydrogen (1H, protium, 2H, deuterium, and 3H, tritium). 

Carbon-14 and hydrogen-3 are radioactive. They are formed by cosmic rays in the upper 

atmosphere. The other isotopes of carbon and hydrogen are stable. Measuring the relative 

concentrations of the isotopes of carbon and hydrogen generally allows the source to be 

distinguished5

. 

Molecular and isotopic analyses combined with a site specific investigation generally provide a 

definitive answer regarding the source of carbon based gases. 
Source Determination - Molecular Analysis 

Different gas sources often exhibit different ratios of gases and isotopic signatures. Results of 

the molecular analysis can be compared to normal atmospheric conditions as shown in Table 1. 

The ratio of components is often useful in determining the source of gas. If the gas constituents 

and ratios between a source and problem area are similar, then further investigation of that 

source is warranted. From Table 1, the residence gas most closely resembles the Backfill 1 gas. 

The data in Table 1 are not all from the same site but are useful in illustrating the typical 

characteristics of gases whose origins are different. Each source will be discussed separately. 

Gas Air Blasting – 

Borehole 

Backfill 1 

with 

Limestone 

Backfill 

2 

Landfill Abandoned 

Mine 

Residence 

N2 78.09% 89.29% 81.09% 78.00% 3.70% 87.77% 80.35% 

O2 20.95% 5.78% 7.29% 19.30% 0.8% 0.30% 9.82% 

Ar 0.93% 1.07% 0.96% 0.93% 1.05% 0.96% 

CO2 0.03% 3.86% 10.65% 1.43% 47.0% 8.96% 8.86% 

CO 0% 0.0023% 0.1% 0% 

CH4 0% 0.0003% 0.013% 0.0087% 47.4% 1.88% 0.15% 

Table 1. Gas samples from various sources. 

Blasting Gases: As discussed earlier, blasting generates elemental nitrogen, CO2, and water. If 

the detonation is not ideal, the blast emits CO and nitrogen oxides. If N2, CO2, and CO 

components of the samples are elevated, the gases may be linked to blasting. Without elevated 

levels of all three, the gases are unlikely to be related to blasting. 

Backfill Gases: Reclaimed surface mines can be a source of CH4 and CO2. Often trees and 

other organics materials are buried. Degradation of this organic material generates both CH4 and 

CO2. The primary precursor of carbon in organic material is CO2 from the atmosphere. 

Occasionally, calcium carbonate (CaCO3) is added to the backfill of surface mines to treat acid 

drainage. When the acidic waters contact the limestone, CO2 is produced. An atmosphere from 

this backfill would be rich in CO2. 

Landfill Gases: CO2 and CH4 generated in landfills are microbial in origin. Occasionally, CO2 

and CH4 from an active landfill may migrate undetected outside of the landfill perimeter. Unpermitted, pre-regulation landfills may also represent CH4 sources with the potential for 

migration to other areas. When these gases are detected, the CH4 component presents a much 

larger hazard than the CO2. 

Abandoned Mine Gases: Gases produced from abandoned mines may be microbial, 

thermogenic, or mixed in origin. Abandoned underground coal mines are CO2 and CH4 sources 

with the potential for migration to areas of lower pressure. In the absence of a mine fire, CO 

should not be present. Fluctuating barometric conditions often drive the migration of CO2 and 

CH4 from shallow abandoned coal mines. Pressure is reduced at the soil/atmosphere interface 

under falling barometric conditions, resulting in soil outgassing. 

In the coal and gas fields, different gas sources generally exhibit different ratios of CH4, C2+ 

hydrocarbons (propane, butane, etc.), and isotopic signatures. The ratio of C2+ hydrocarbons is 
often useful to determine if the gas is microbial or thermogenic in origin. High concentrations of 

C2+ hydrocarbons are an indication that the gas is thermogenic in origin. However, the absence 

or low concentrations of C2+ hydrocarbons do not indicate the gas is microbial in origin9

. This 

is due to other processes that may affect the composition of the gas during migration such as 

fractionation, ie. removal or impediment of the heavier hydrocarbons as gas migrates through the 

soil column, or bacterial oxidation, the consumption or conversion of the C2+ hydrocarbons. 

When combined with other elements of an investigation, stable carbon and hydrogen isotopic 

analyses provide powerful analytical tools to distinguish microbial and thermogenic hydrocarbon 

gas sources and stable carbon isotope analysis of stray CO2 also yield data to determine if the 

source is organic or inorganic in origin10. 

Source Determination – Isotopic Analysis 

Stable carbon isotope geochemistry provides a valuable analytical tool to determine the origin of 

stray CO or CO2. Isotopes are atoms whose nuclei contain the same number of protons but a 

different number of neutrons. Stable isotopes are not subject to radioactive decay. Their 

abundance in nature is controlled by other biological and physical processes, such as 

photosynthesis in the case of stable isotopes of carbon (12C and 13C). Sedimentary carbonates 

and organic matter possess discrete stable isotopic characteristics because of the operation of two 

different reaction mechanisms8. 

1.	 Isotope equilibrium exchange reactions within the inorganic carbon system lead to an 

enrichment of 13C in carbonate rocks. 

2.	 Kinetic isotope effects during photosynthesis concentrate 12C in organic matter. 

13C/12C values are expressed in parts per thousand or per mil (o/oo). The standard is the 

internationally recognized PDB reference standard for carbon. This standard is from a 

cretaceous marine fossil, Belemnitella Americana from the PDB formation in South Carolina. 

The PDB standard has been assigned a value of 0 per mil. Negative numbers signify enrichment 

in the lighter isotope (12C) relative to the standard whereas positive numbers signify the carbon is 

enriched in the heavy isotope. Atmospheric CO2 has a value of -8 per mil. 

Isotopic analyses allow differentiation between microbial, thermogenic and organic and 

inorganic sources of carbon based gases. For example, CH4 from a coalbed will often have a 

different stable carbon isotopic composition when compared to CH4 from an active or abandoned 

gas well. 

Stray CO2 can also be traced to its source through isotopic analysis. CO2 derived from an 

inorganic source (limestone) is typically enriched in the heavier isotope (13C). Whereas, CO2 

derived from an organic source (degradation of organic matter) will be enriched in the lighter 

isotope of carbon (12C). In blasting the carbon source is diesel fuel (CH2) and is expected to be 

enriched in the lighter isotope of carbon. When the lighter isotope is predominant and the source 

is still uncertain (microbial or thermogenic), 14C analyses can provide the final clue. 

Where microbial gas is suspected as the potential source, 14C analyses provide definitive results. 

Recently formed gases, such as landfill gases, are enriched in 14C, and are readily distinguished 

from thermogenic sources9

. Thermogenic CH2 was formed from organic materials that are 
millions or hundreds of millions of years old and does not contain any detectable 14C. Stray gas 

derived from diesel fuel will have no 14C activity. 

Summary 

Carbon based gases, carbon monoxide and carbon dioxide, are produced in the detonation of 

explosives. Historically gases have been documented to travel through the ground up to 500 feet 

from the blast site. When these gases enter confined places where either workers or the public 

occupy the space, they may become overcome by gas. As blasting occurs in close proximity to 

work place confined spaces, like manholes, workers should be trained on the physiological signs 

of gases prior to blasting and during blasting. Testing of the work areas should also be 

conducted prior to entry. When blasting near public places, like homes, public education on the 

physiological signs of gases are best conducted during preblast surveys. On some occasions the 

blaster may be wise to offer commonly available in-home gas detection devices to the occupant. 

The aerial extent of concern should be tied to the local geology and subterranean man-made 

features. 

If carbon gases are identified at any time, they may be attributed to blasting activities in the 

vicinity. Initial gas sampling consists of taking field samples to identify dangerous environments 

and ensuring the safety of the public. If CO or CO2 concentrations exceed 9 ppm or 0.5%, 

respectively, a detailed investigation is recommended. 

Detailed investigations include continuous monitoring and the collection and analysis of gas 

samples. Continuous monitoring provides a time history of gas concentrations that may relate to 

nearby activities or environmental changes such as barometric pressure swings. Clues of the 

driving mechanism may be found. Laboratory analysis of gas samples will provide detailed 

information on the molecular composition of the stray gas and nearby potential sources. When 

compared to each other, the source may become obvious. However if the molecular results 

prove inconclusive, isotopic analyses can be conducted to more clearly identify the gas source. 

Site specific investigations combined with molecular and isotopic analyses and knowledge of the 

relative amounts of basic gases common in mine backfills, landfills, blasts, and abandoned 

mines, provide a comprehensive approach to identify the source of a stray gas. 

References 

1

 Eltschlager, K. K., W. Shuss, T. E. Kovcalchuk, “Carbon Monoxide Poisoning at a Surface 

Coal Mine ... A Case Study”, In: Proceedings of the 27th Annual Conference on Explosives and 

Blasting Technique. Orlando, FL: International Society of Explosives Engineers. 

2

 Santis, LD, “A Summary of Subsurface Carbon Monoxide Migration Incidents”, In: 

Proceedings of the 27th Annual Conference on Explosives and Blasting Technique. Orlando, FL: 

International Society of Explosives Engineers, pp. 133-141. 

3

 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. 
4

 Baldassare, A. J., K. Eltschlager, “Stray CO2 Investigation, Gray Residence, Derry, 

Westmoreland County, Pennsylvania”, File Report - Pennsylvania Department of Environmental 

Protection, December 23, 2003. 

5

 Eltschlager, K.K., J. W. Hawkins, W. C. Ehler, F. Baldassare, Technical Measures for the 

Investigation and Mitigation of Fugitives Methane Hazards in Areas of Coal Mining, Office of 

Surface Mining Reclamation and Enforcement, September 2001. 

6

 “NIOSH Pocket Guide to Chemical Hazards – Carbon Monoxide,” 

http://www.cdc.gov/niosh/npg/npgd0105.html accessed November 5, 2003. 

7

 “NIOSH Pocket Guide to Chemical Hazards – Carbon Dioxide,” 

http://www.cdc.gov/niosh/npg/npgd0103.html accessed November 5, 2003. 

8

 Hoefs, J., Stable Isotope Geochemistry, Springer-Verlag, 1997 

9

 Coleman, D., “Advances in the Use of Geochemical Fingerprinting for Gas Identification”, 

Colorado Oil and Gas Conservation Commission and Bureau of Land Management, 

San Juan, 1994 

10 Baldassare A. J., C.D. Laughrey, “Identifying the Sources of Stray Methane by Using 

Geochemical and Isotopic Fingerprinting”, Environmental Geosciences, vol. 4, no. 2, pp 85-94, 

1997