No. 488 May 2001

Migration of Blasting Fumes Into a 

Western Pennsylvania Home

Background

Carbon monoxide (CO) is an odorless, colorless gas that can

cause illness and death by asphyxiation. Although the toxicity of

CO is understood, CO exposure can occur from unrecognized

sources. On April 2, 2000, a couple and their newborn infant were

poisoned by CO migrating through the ground from blasting at a

nearby coal strip mine into their home near Kittanning, Armstrong

County, PA. They were treated at the hospital and diagnosed with

CO poisoning. The infant had a carboxyhemoglobin level of 31%,

the father 28%, and the mother 17%. Carboxyhemoglobin is the

compound formed in the blood when CO is breathed. Persons not

exposed to CO have carboxyhemoglobin levels of 0.3%-0.7%, and

cigarette smokers have levels of up to 9%. Following release from

the hospital, the family installed a CO detector in the basement of

their home with the help of the local fire department. This

Technology News briefly describes this incident to help increase

awareness of the problem. It is discussed in more detail by

Eltschlager et al. [2001].

Figure 1 shows the coal strip mine believed to have generated

the CO. The initial suspect for the source of the CO was the

furnace in the house. Only later did it become apparent that

blasting at the nearby strip mine might be the culprit. A State

investigation concluded that CO had migrated approximately 500

ft from the blast, through the ground, and into the home.

Figure 2 shows the locations and order of blasts at the mine.

Initially, the mine did not plan to blast. Overburden generally

consisted of weathered shale that could be dug without blasting.

However, the mine decided to blast when hard sandstone that could

not be dug out was encountered within 3 ft of the coal top. The

blastingwas intended to break up the sandstone. Blasting was done

using bulk ammonium nitrate-fuel oil (ANFO) in 6.25-in holes 25-

30 ft deep on a 16-ft by 16-ft pattern, with charge weights ranging

from 17 to 170 lb. The closest blast to the home was 430 ft on

April 17, 2000. The distance from the home to the blast area on

the day when CO was first reported (March 31, 2000) was 500 ft.

Twenty blasts 

were detonated at the mine between March 7, 2000, and April 20,

2000. The blaster was careful to prevent flyrock since another home

was only 150 ft away and a garage was 50 ft away. The quantity of

explosive used in the blastswassufficient to break the sandstone, but

was less than would normally be used to blast overburden. The holes

were typically one-third explosive and two-thirds stemming, with

powder factors averaging 0.43 lb/yd3. Additionally, the muck was

not immediately excavated after each blast. The heavy confinement

on the explosive acted to prevent the typicalrelease of blasting fumes

into the atmosphere.

Instances of CO migrating from blasts into homes have occurred

before, but generally the distances involved were under 150 ft. It is

believed that the blast design contributed to the confinement of CO

in the ground, and discontinuities in the ground strata facilitated

migration toward the residence. Upon inspection of the blast pit

wall, a regular system of joints was observed. These joints are

oriented roughly from the blast pit toward the house (figures 3-4).

Blast-generated CO appears to have been driven into the joint

system, displacing the air. When the joint system was saturated, the

nextsucceeding blast pushed the CO into an uncased well next to the

house (a high level of CO has been measured in thewell shortly after

a blast). From there, the CO entered the French drain system and

then the basement of the house.

The joints are vertical cracks through rock layers that occur on a

regular spacing (figure 3). They are most common near valley

slopes and are caused when valley walls converge as the stream cuts

down through the rock layers. Often called hillseams, they roughly

parallel the valley walls, but can curve and split, creating a pathway

for gas movement (figure 5). These fractures are often encountered

when underground mining proceeds close to outcrop. The system of

fractures at the Kittanning blast pitwaswell developed and provided

a path for transmission of CO both through the sandstone and up

and through the overlying shales. Blasting engineers should be able

to distinguish naturally occurring fractures from blast fractures and

note the frequency, development, and orientation of the hillseams

and their proximity to occupied houses. The limits of transmission

o f
 Figure 1.— Blasting in this coal strip mine generated CO that is believed to have poisoned nearby residents.

blast-generated CO through naturally occurring fractures are not

known, so blast engineers should proceed with caution near

residential areas.

Recommendations

(1) When blasts are heavily confined, blasters should examine

the blast site for any indicators that would identify the presence of

underground pathways for CO migration.

(2) The blast should be excavated as soon as practical following

detonation.

(3) Blasters should be aware that CO can travel through the

ground to basements of homes or other confined spaces and take

adequate precautions. Placing CO monitors and alarms in homes

where this potential exists would be prudent.

For More Information

For additional information, contact Richard J. Mainiero,

Ph.D., phone: (412) 386-6625, e-mail: rom6@cdc.gov, or Gregory

M. Molinda, phone: (412) 386-6890, e-mail: gdm4@cdc.gov.

References

Eltschlager KE, Shuss W, Kovalchuk TE [2001]. Carbon

monoxide poisoning at a surface coal mine: a case study. In:

Proceedings of the 27th Annual Conference on Explosives and

Blasting Technique. Vol. II. Cleveland, OH: International Society

of Explosives Engineers, pp. 121-132.

To receive additional information about occupational safety

and health problems, call 1-800-35-NIOSH(1-800-356-4674),

or visit the NIOSH Web site at www.cdc.gov/niosh

Mention of any company name or product does not constitute

endorsement by the National Institute for Occupational Safety

and Health.
 Figure 2.— Map showing blasting at the strip mine and the location of nearby residents. The

house labeled "Residence #1" is where the family suffered CO poisoning.

 Figure 3.— Fractures (hillseams) in the pit wall marked with arrows. The fractures are oriented toward

the house.
 Figure 5.— This photo from another site shows a hillseam

discontinuity. Figure 4.— A hillseam is a zone of fractures that cuts the

sandstone.