CO Migration from Trench Blasting in Amherst, New York 

by Marcia L. Harris and Richard J. Mainiero 

Abstract 

The New York State Department of Transportation recently commenced highway widening and 

drainage improvement projects in Clarence and Amherst, NY. Drainage improvements 

including the installation of storm sewer lines required excavation to a depth of 2.5 m (8.2 ft). 

In September 2002, NYSDOT stopped further blasting when 800 ppm CO was detected in the 

basement of a house near the blasting site. At the insistence of NYSDOT, the general contractor 

developed a new blast plan with the assistance of an environmental consultant. The plan 

provided for the installation of multi-gas monitors in buildings of special concern and/or with 

basements and residential type CO monitors in all other buildings within 100m (330 ft) of the 

blast. The multi-gas monitors would be remotely monitored. The plan provided action levels 

which would ensure public safety. The blast design was also modified to allow for better venting 

of CO. Blasts were limited to 20 ft lengths. The overburden was to be removed from the rock 

and blasting mats put in place to prevent flyrock. Approximately twenty feet of trench adjacent 

to the blast was left open to allow ground movement and gas release. 

The use of CO monitors was effective to alert occupants of a building to the presence of CO. 

The most effective appeared to be the residential type CO alarms with digital readouts. They 

were simple and easy to use and allowed the public to participate in the process. False alarms 

were repeatedly received with the more sophisticated instrumentation. Residential type CO 

monitors are preferable to warn people near blast sites. More sophisticated instrumentation 

should be avoided unless personnel are experienced in its use. 

A general overview of the blasting and monitoring is presented and discussed. The use and 

effectiveness of residential type CO monitors and multi-gas monitors are discussed. 
Introduction 

Toxic gases such as carbon monoxide (CO) and nitrogen oxides (NOx) are produced by the 

detonation of explosives. The implications and minimization of such products have been studied 

for decades. 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 vent to the atmosphere. 

The NYSDOT has recently commenced two consecutive reconstruction projects on the same 

highway corridor. The contracts were awarded to two different prime contractors. Both projects 

included the installation of new storm sewer lines, requiring removal of bedrock and both prime 

contractors hired the same blasting subcontractor to break up the limestone bedrock. Beginning 

in April of 2002, carbon monoxide (CO) was detected in homes and businesses near the blast site 

in Clarence, NY. NYSDOT contacted their consultant to screen the structures in the vicinity of 

the blasting operations and assist in determining the possible cause and migration routes of the 

CO. In May of 2003, NYSDOT asked NIOSH for assistance with this problem. NIOSH 

personnel traveled to Amherst on several occasions to view the incident site, study the data, and 

advise NYSDOT personnel on techniques for minimizing the movement of CO. NIOSH 

personnel plan to combine the information collected at this and similar sites with the results of 

NIOSH research to develop guidelines to minimize the possibilities of workers or the public 

being injured by CO from blasting. Migration of CO from a blast into nearby structures is not a 

common occurrence but has been observed and reported.1,2,3,4,5

Excavations for installation of sewer lines along the street required that a trench be excavated to 

a depth of 2.5 to 4.5 m (8.2 to 14.8 ft). Hard Onondaga limestone was encountered at a depth of 

about one meter (3.3 ft). The hardness of the limestone was one of the reasons the contractor 

chose to use blasting as the primary method of breaking up the rock. Mechanical means of 

breaking the bedrock were also employed, but were less effective and efficient in some areas. 

Background 

NYSDOT first became aware of the occurrence of CO migrating into homes and businesses on a 

Clarence, NY, Erie County project in April 2002. On April 9, a homeowner near the excavation 

site reported that a CO alarm indicated elevated levels of CO were present in his two-story frame 

house. The homeowner and the NYSDOT Engineer in Charge (EIC) of the project suspected 

that blasting may have caused the elevated CO readings. Later in the day, NYSDOT’s 

environmental consultant visited the home and detected 57 ppm CO in the basement. Further 

investigation was inconclusive as to the cause of the elevated CO in the residence. On April 10, 

another nearby resident in close proximity to the blast site reported that a CO monitor in the 

basement had alarmed. The consultant visited the home and five others nearby and measured for 

CO. Although no significant CO was detected, the NYSDOT EIC and the Construction 

Environmental Coordinator (CEC) asked the consultant to purchase and install CO monitors in 

the six homes. The following day, five more CO monitors were purchased and installed. 

Blasting and CO monitoring continued through April, May, and June 2002. The highest CO 

levels detected were 318 ppm and 111 ppm on May 30 and 31 in the basement of one business. 
The building was ventilated by opening doors and windows. No CO was detected in any of the 

other homes or businesses monitored during this time period. However, awareness of blasting 

related CO was raised. 

In August 2002, the NYSDOT commenced a second reconstruction project involving another 

area of the same highway corridor, in the town of Amherst, NY, Erie County. Due to the 

concerns on the previous project regarding the possible generation and migration of CO, the 

NYSDOT EIC and CEC requested the NYSDOT’s environmental consultant to install CO 

monitors in basements or crawl spaces in nearby structures. Initially three CO monitors were 

employed, with five more being purchased the next day. The monitors were installed in 

basements or crawl spaces of eight nearby homes. The monitors were moved as the blasting 

progressed. NYSDOT’s environmental consultant checked the monitors on a daily basis, 

simultaneously taking readings with a real time quad-gas monitor. Table 1 contains summary 

information on the CO incidents. 

Table 1 – Summary information on CO detected. 

Date 

Location Of CO 

Monitor 

Peak CO 

Reading 

Time Elapsed 

Since Last Blast 

Last Blast Total 

Explosive Weight 

8/28/02 Basement, adjacent to 

sump pit 213 ppm Approximately 14 

hours 1030 lb (467.2 kg) dynamite 

9/12/02 Basement, adjacent to 

foundation crack 67 ppm Approximately 12 

hours 

9/12/02 Residence beyond 100 

Meters from blast zone 90 ppm Approximately 16 

hours 

165 lb (74.8 kg) dynamite 

400 lb (181.4 kg) ANFO 

9/20/02 Basement, adjacent to 

sump pit 800 ppm Approximately 18 

hours 

110 lb (49.9 kg) dynamite 

275 lb (124.7 kg) ANFO 

The first occurrence of CO on this project, took place August 27, 2002, see Figure 1, and was 

attributed to an automobile running in the garage. The first definite sign that CO was migrating 

from the blasting occurred on August 28, 2002, when 213 ppm was recorded in a basement. This 

incidence was followed by two occurrences of elevated CO recorded on September 12. In the 

first instance, the CO alarm located in the basement adjacent to a crack in the foundation alarmed 

when the concentration of CO peaked at 67 ppm. In the second instance on September 12, a 

resident living just beyond 100 meters from the blasting area contacted the EIC to report their 

own CO monitor had been periodically alarming. They initially disregarded the alarm. An 

investigation disclosed that CO was present in an unlined sewage ejection pit in the basement at 

90 ppm. This appeared to be the avenue by which the CO entered the home. No other source of 

CO was identified. 

At 2:00 AM on September 20, 2002, the CO monitor in a group home located along the project 

corridor sounded. A CO reading of 800 ppm was present in the basement at that time. The fire 

department was contacted and the building was evacuated. The NYSDOT environmental 
consultant later surveyed the home for CO. The only CO detected was near the sump in the 

basement. The sump was covered with plastic and the environmental consultant measured 70 

ppm in the vicinity of the sump several hours later. The NYSDOT and their environmental 

consultant were able to positively identify the sump as the point of entry. No other sources of 

CO were evident. 

These occurrences of blasting-generated CO migration revealed a pattern of CO building in the 

ground and then migrating to a point of escape, such as a sump pit. The inability to force people 

living along the project corridor to react to the CO monitors, or in some cases, to initially accept 

the monitors, concerned NYSDOT personnel. Concerns were also raised regarding the 100 

meter threshold for CO migration. 

On September 23, 2002, NYSDOT told the construction and blasting contractors that blasting 

could not resume until a new blasting plan was developed that better addressed the issue of CO 

migration. During late September and October, three proposed blasting plans were reviewed and 

rejected by NYSDOT. The plans were rejected due to lack of clarity, comprehensiveness, and 

likelihood of controlling the generation and migration of CO. The project work slowed at this 

time due to winter shutdown. In the spring of 2003, the contractor used mechanical means to 

break the rock for removal. This practice worked well in some areas but proved highly 

inefficient in others. 

Because blasting of the bedrock was the method chosen by the contractor, the NYSDOT 

emphasized that the contractor needed to take a more active role in the monitoring process and in 

the risks and uncertainties associated with blasting and CO migration. This request was granted. 

The contractor submitted a new blasting plan in early May 2003, that included taking on 

responsibility for monitoring. After significant discussion and revisions, it was approved on 

May 14, 2003. The blasting plan specified that prior to a blast, the contractor’s environmental 

consultant would survey each building within 100 meters (330 ft) of the blast. This survey 

would: 

1) indicate whether each house had a basement or was built on a slab, 

2) identify potential pathways for toxic gases to migrate into the structure (e.g. gas lines, 

water lines, sewer lines, telephone lines, etc), 

3) provide each owner/resident with a notification letter, 

4) contact the owner or resident of each structure, conduct an internal inspection to identify 

the locations where toxic gases could enter the structure (e.g. sumps or dry wells), and 

identify any special conditions/uses, 

5) determine the type(s) of air monitoring equipment that should be installed in each 

structure and the location(s) where the monitoring equipment should be installed, and 

6) identify other potential sources of toxic gases. 

Identification of a slab or basement construction was thought to be an indication of susceptibility 

to CO migration. Typically, potential entry points such as sumps or drains are located in a 

basement. Slab construction would not have these potential entry points. Previous blasting 

revealed 4 out of 5 high readings occurred in homes with basements. Routes of entry included 

sumps and a sewage ejector pit. 
The blasting plan also required that toxic gas monitoring instrumentation be employed. The 

contractor’s environmental consultant set up five AreaRAE monitors 

(http://www.raesystems.com/area.html) in five buildings of special concern for continuous 

remote monitoring of CO, nitrogen dioxide (NO2), and oxygen (O2) concentrations.♦ The 

AreaRAE monitors are electrochemical-cell based instruments that sample every 2 minutes and 

radio transmit the data to a central laptop computer. Nighthawk CO monitors were also placed 

in each home and business within 100 m (330 ft) of the blast.♦ The Nighthawk CO monitors 

were intended to alert residents in the event that the CO concentration reached levels of concern. 

These units were designed to alarm within 90 min at 100 ppm CO, 35 min at 200 ppm CO, and 

15 minutes at 400 ppm CO.6

 The Nighthawks also recorded the peak CO level occurring since 

the last time they were reset. Periodically, the consultant’s personnel would check the 

Nighthawks and reset them. The NYSDOT environmental consultant continued to act in an 

advisory and backup monitoring capacity. The AreaRAE multiple gas detectors were to be put in 

place at least 24 hours prior to blasting. Action levels were set at 9 ppm for CO and 0.25 ppm 

NO2. If concentrations exceeded the action levels, the person monitoring the instrumentation 

was to notify a contact person in the affected building, the fire department, the contractor, and 

NYSDOT. The instrumentation is illustrated in Figure 2. Figure 3 shows the placement of toxic 

gas monitoring instruments and the location of the first blast. 

The first blast was scheduled for the morning of May 15, 2003 (see Figure 7). On the evening of 

May 14, the environmental consultants for the contractor and NYSDOT set up the AreaRAE and 

Nighthawk monitors. The consultant for NYSDOT also spoke with the residents and explained 

the functioning and purpose of the monitors; he reported that all the residents were receptive and 

cooperative. In the early morning hours of May 15, the AreaRAE at the Youth Center alarmed 

when it detected 0.4 ppm NO2. Following an investigation it was determined this was a false 

alarm and the NO2 alarm level was reset to 1 ppm. 

The first blast was conducted at approximately 11:00 AM on Thursday, May 15, 2003. The blast 

consisted of ten holes, twelve to fourteen feet (3.7 to 4.3 m) deep, each loaded with four or five 

2.25- x 16-in. cartridges of dynamite and seven feet (2.1 m) of stemming. Interval blasting 

involving the removal of the overburden from the rock and the blasting of 20 feet (6 m) sections 

into an open trench was employed to allow for easier release of explosive fumes. Blasting mats 

were placed on the shot to prevent flyrock. Steel plates were also placed over the open trench 

end to minimize flyrock. All shot rock would be excavated immediately following detonation of 

the blast. The excavation would be left open to allow the toxic gases generated from the blasting 

operations to vent. Figures 4, 5, and 6 illustrate the setup for the blast. A total of four blasts 

were conducted on May 15, followed by four blasts on May 16. 

Over the weekend of May 17-18, the AreaRAEs alarmed several times for NO2 but an 

investigation of the alarms attributed them to either response of the NO2 sensor to chorine bleach 

in a laundry room, a software setup error, or a calibration error. No significant CO was detected. 

Blasting resumed on Monday, May 19. 

 

♦ Use of brand names is for informational purposes only and does not imply endorsement by NIOSH. 
Blasting continued without incident until May 28 when 6 ppm CO was detected in the youth 

center. An investigation revealed that CO was entering the building through a basement sump 

pit in a storeroom and through cracks in the floor under a sink. A window fan was installed to 

help ventilate the storeroom area. 

In the early morning hours of May 29, a check of the youth center revealed 35 ppm CO in the 

sump pit. In an effort to keep CO out of the building, plastic was taped over the sump and the 

cracks under the sink were sealed with duct tape or caulk. At about 10:00 that morning, 400 ppm 

CO was detected in the sump pit. By noon the CO in the sump pit had risen to more than 1,500 

ppm. NYSDOT suspended blasting operations because the blasting plan had failed to prevent 

migration of CO into the youth center. A vent pipe and additional fans were employed to reduce 

the levels of CO in the basement. 

On May 30, a meeting was held to discuss revisions to the blasting plan that would aid in 

preventing future CO migration. The participants at the meeting believed that CO migration had 

become a problem because the blaster gradually raised the number of shots from four a day (165 

– 200 lb [74.8 – 90.7 kg] dynamite per shot) to six a day (170 – 300 lb [77.1 – 136.1 kg] 

dynamite per shot), and possibly leaving insufficient time to vent the CO between blasts. To 

address this, the blasting plan was revised to provide for shooting alternately at two different 

locations, allowing the CO more time to vent between blasts. The revised plan required at least 

three hours between each blast in one area. Each area was to be a minimum of 300 meters apart. 

No more than 4 blasts in one day were to be allowed. Additionally, ventilation holes were dug 

down to any utility lines along the right-of-way within 100 m (330 ft) of the blast. These vent 

holes were intended to both provide venting of the CO and track the migration of the CO. Other 

parts of the blasting plan were also revised based on the experience gained during the previous 

month. 

The blast plan was revised and blasting resumed on June 17, 2003. Blasting continued with low 

level CO migration occurring. CO readings were recorded ranging from 0.4 ppm to 1.1 ppm. 

On June 21, 2003, the contractor’s operations were suspended in one of the two blasting areas, 

by National Fuel Gas, due to elevated seismic displacement. The contractor requested that 

blasting be increased in the remaining area. NYSDOT denied this request. The current approach 

of blasting in two alternate areas appeared to be keeping CO migration to a minimum. 

It was agreed to allow the contractor to blast in one area with the condition that they install 

standpipes at routine intervals in the previously blasted trenches to allow any trapped CO to vent. 

The standpipe was a 24 inch PVC pipe surrounded by pea gravel. The pipe was placed in 

previously blasted and broken up rock at a depth equivalent to the bottom elevation of the blast. 

The standpipe was placed as close as possible to the area being blasted. See Figure 8 for details. 

The standpipe appeared to allow the CO a direct venting pathway. Levels ranging from 30 ppm 

to 1500 ppm were recorded at the standpipe. At the urging of NYSDOT and their environmental 

consultant, the contractor began ventilating the standpipes after blasting, to attempt to remove 

the CO before it migrated. At one point, in an effort to reduce CO levels faster in the trench, the 

contractor excavated a vent pit next to the standpipe. 
The level of CO was monitored at both utility lines and the standpipes. When the level of CO 

was below 200 ppm, and at least three hours had passed, blasting would resume. If 200 ppm or 

more CO was measured at any monitoring point (house, office building, utility line, standpipe, 

etc.), or the three hours had not elapsed, no blasting was allowed. Utilizing the standpipe, vent 

pit and ventilation strategies continued even after blasting in two different areas resumed. 

Discussion

In an effort to prevent CO migration from the blasting site to the nearby structures, NYSDOT, 

the general contractor, and the environmental consultants agreed upon a blast plan that detailed 

not only the blasting activities, but the pre-blast excavation preparations, toxic gas monitoring 

efforts, and necessary emergency response and notifications. Information collection activities 

were detailed in the blast plan. This included pre-blast surveys of all buildings within 100 m that 

would identify potential sources of entry. Internal inspections of the potentially affected 

structures would be performed. Potential pathways such as utility lines would be identified. The 

blasting approach was defined as interval blasting and the explosives to be used were required to 

be IME Fume Class 1. The removal of overburden and use of blast mats was specified in the 

blast plan. Immediate excavation of shot rock was also required. Utilizing a standpipe as a 

venting mechanism was also later employed. In the event of high readings or an alarm on the 

gas monitoring equipment, an action plan for the occupant and the remote monitoring person was 

also developed. 

Some valuable lessons were learned from the blasting discussed here. A major difficulty in the 

May, 2003 blasting was false alarms by the instrumentation. There were several causes for this. 

• Failure to install the AreaRAE units 24 hours prior to the first blast. This may have 

revealed some of the non-blasting related causes for the NO2 sensor alarm, which would 

have aided in preventing false alarms. 

• The alarm levels for the NO2 and CO measured using the AreaRAE units were set too 

low. 

• Difficulties in the use of the AreaRAE units. 

The AreaRAE instrumentation is based on electrochemical cell science. Users of the 

instrumentation should have experience with the instruments. The accuracy of the 

instrumentation should be known, any chemical interactions that may trigger a false reading 

should be known, and the instrument capabilities in general should be well understood. 

Typically, household CO monitors are designed to alarm when exposed to a given CO 

concentration for a set period of time. The alarm level is set to provide adequate protection 

while minimizing false alarms. Underwriter Laboratory (UL) recommendations for CO alarm 

levels for home CO monitors are detailed in UL2034.7

 This philosophy should also apply to CO 

produced by blasting. Once CO migrates into a home, it is no different from CO produced by a 

faulty furnace or gas appliance. Rather than developing alarm levels to apply to the detection of 

CO from blasting, it would seem reasonable to use UL’s standard, as detailed in Table 2. In 

short, commercial home CO monitors seem to be the most appropriate instrumentation for 

protection from CO migrating from a blast into a nearby structure. Use of more sophisticated 
instrumentation by persons who are not experienced in their use may lead to errors and confusion 

that mask dangerous CO levels. 

Table 2 - Underwriter Laboratory’s recommended alarm levels for home CO monitors.7 

CO Concentration, ppm Time Until Alarm Sounds 

15 30 days 

70 189 min (minimum 60 min) 

150 50 min (minimum 10 min) 

400 15 min (minimum 4 min) 

For the project reported here, NO2 was monitored along with CO because it is theoretically 

possible that NO can migrate through the ground along with CO and oxidize to NO2 when it 

enters a confined space. Small yellowish-orange clouds were observed after some of the blasts. 

This is confirmation that NO and NO2 were being produced in the detonation production 

gases.8,9,10 Monitoring appears to confirm, in this instance, the migration of NOx was not an 

issue of concern within the structures. 

A factor that can be controlled and can contribute significantly to the CO produced by the blast is 

the oxygen balance of the explosive used. Figure 9 shows that the CO production of ANFO 

increases significantly as the oxygen balance becomes more negative.11 This is confirmed in 

Explosives and Rock Blasting which states “An excess of oxygen in the explosives can result in 

the formation of nitrogen oxides (NO and NO2) and a deficit of oxygen can cause carbon 

monoxide (CO) to form.”12 This means that an explosive formulated with too much fuel will 

produce excessive CO. An explosive formulation with too little fuel will generate excessive 

nitrogen oxides. 

The ISEE Blaster’s Handbook recommends, “Where fumes can be a problem, proper formulated 

and manufactured explosives and blasting agents will give minimum quantities of toxic gases.”13 

If ANFO is mixed on site, the blaster should ensure that the ratio of fuel oil to ammonium nitrate 

is correct. However, the blaster has no control over the formulation of premixed explosive 

products. For premixed products, only the manufacturer can control the formulation. The 

manufacturer must ensure that the explosive is properly formulated to minimize toxic fumes 

production. 

At Amherst, a number of techniques were employed to help minimize CO migration. These 

included: 

• shooting into an open pit to allow the broken rock to expand and vent toxic gases, 

• removing the overburden prior to blasting and the shot rock after blasting, 

• alternating blasting areas to allow sufficient time in between blasts for CO to vent and 

dissipate (limiting the amount of explosives used at any one site and in any one day), and 

• installing standpipes in close proximity to the blast site and ventilating these standpipes 

until a lower level of CO was measured. 
These methods seem to have allowed the continuation of blasting with minimal CO migration 

occurring and with minimal public involvement. Two instances show the complexity and the 

possible necessity of each of the involved factors. 

1. On June 30, 2003, the concentration of CO in a standpipe prior to loading the shot holes 

for the second blast of the day, was 16 ppm. The concentration of CO rapidly rose to 

over 700 ppm as soon as ventilating activities were discontinued. This is when the 

contractor began excavating a vent pit next to the standpipe. 

2. The last two blasts of the Amherst project contained deviations from these procedures. 

The area being blasted was across the roadway. Therefore, to minimize the impact on 

traffic, the overburden was not removed prior to blasting. The roadway location also 

lacked the area needed for a standpipe or vent pits. It was determined that the storm 

sewer manholes, installed on both sides of the roadway, would be monitored for CO. It 

was also decided that the number of shot holes would be limited to reduce CO generation. 

CO in the storm sewer prior to blasting was 0 ppm. CO readings about 1 1⁄2 hours after 

the blast exceeded 1500 ppm. The contractor began ventilating the storm sewer. 

Ventilation brought the levels of CO in the storm sewer manholes down to 425 ppm on 

the north side and 580 ppm on the south side of the roadway within the next half hour. 

The two instances illustrate how the CO may be produced and travel to the point of least 

resistance. 

Another factor that seems to have impeded the migration of CO is the limitation of explosives 

used within a day in any one area. CO appeared to migrate again, at low levels, when the 

contractor went back to blasting in one area. The use of standpipes also appeared to have 

mitigated CO in the ground before it could potentially migrate to an enclosed space. 

For the blasting discussed here, factors seemed to gradually change from shot to shot. The 

prevention techniques employed appeared to curtail the CO migration successfully in this case. 

However, one cannot say for certain which contributed to or minimized CO migration. One 

cannot say that the changes to the blast plan prevented CO migration for a given shot because the 

blaster had probably used the original blast plan previously for hundreds or thousands of shots 

without a known case of CO migration 

Summary 

The use of CO monitors was effective to alert occupants of a residence to the presence of CO. 

The most effective appeared to be the residential type CO alarms with digital readouts. They 

were simple and easy to use. False alarms were received with the more sophisticated 

instrumentation related to lack of in-depth experience in its use in this application. Residential 

type CO monitors have provided the best early warning to people near blast sites. More 

sophisticated instrumentation should be avoided unless personnel are experienced in its use. 
Although many factors changed over the course of the project in Amherst, NY, it appears that the 

following factors contributed to minimizing the buildup and migration of CO in this location, in 

this type of bedrock: 

• researching the characteristics of the bedrock and the overburden in the area; 

• surveying and monitoring all structures within 100 meters of the blast; 

• limiting the amount of explosives and the frequency of blasting in any one area within a 

day’s time; 

• removing the overburden prior to blasting and using blast mats; 

• excavation of the shot rock after detonation; 

• utilizing standpipes in close proximity to the blast area; and 

• ventilation of the standpipe when CO was detected. 

As the blasting continued, the location and circumstances changed. When numerous factors are 

changing simultaneously, it is not possible to say which one caused a given outcome. This is a 

complex issue and circumstances in a particular area need to be handled individually. 

Acknowledgements 

The assistance of Janine Shepherd and Kim Silvestro of New York State Department of 

Transportation and Scott McCone of URS Consultants, Inc., is gratefully acknowledged. Their 

contribution of data and input are greatly appreciated. 
Figure 1 - Area blasted during August and September, 2002. Pad and Base indicate 

whether the corresponding home is built on a pad (slab) or has a basement. The dates and 

the number of blast holes are indicated. Each blast hole was loaded with three to four 

pounds of ANFO. 

Figure 2 - AreaRAE and Nighthawk gas monitors. 
Figure 3 - Locations of instrumentation for May 15, 2003 blast. 

Figure 4 - Steel plates cover the open trench area. 
Figure 5 - Overburden is removed from the rock. 

Figure 6 - The blast was designed so the broken rock could move into the excavated space, 

allowing the gases to vent. 
Figure 7 - Locations of blasts during May, 2003. 

The vent pit and pipe were placed as close to the blasted area as possible.

The maximum distance is 20 m to vent pit and 30 m to vent pipe from blast area.

Blast Mats

Vent Pit

24“

slotted pipe

3- 5 m 7 m

Washed Pea Gravel (6“ wide)

Previously

Shot Rock

2 m

Figure 8 - Final Blast Layout. 
Figure 9 - Effect of Oxygen Balance on carbon monoxide production for 94/6 ANFO and 

high explosives (cap-sensitive explosives).7 

 

References 

1

 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. 

2

 Mantel, RL 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

 Mainiero, RJ, Technology News 488, Migration of blasting fumes into a western Pennsylvania 

home: U.S. Department of Health and Human Services, Public Health Service, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and Health, 2001. 

4 Eltschlager, KK, W Schuss, TE Kovalchuk, 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, 2001. 

5 Decker, JA, S, Deitchman, L Santis, Hazard Evaluation And Technical Assistance Report: 

Carbon Monoxide Intoxication and Death in a Newly Constructed Sewer Manhole, NIOSH 

HETA 98-0020, 1998. 

6

 Safety Products Unlimited “Kidde Nighthawk Premium Plus Carbon Monoxide Alarm,” 

http://www.safetyproductsunlimited.com/co_alarm.html accessed September 22, 2003. 

7

 Standard for Single and Multiple Station Carbon Monoxide Alarms, Underwriters Laboratory, 

Second Edition, October 29, 1996. 

8

 Agreda, C, Rock Blasting Environmental Impacts. International Society of Explosives 

Engineers, 1995 v1 G, 2000, p. 143. 
9

 Turcotte, R., R Yang, MC Lee, B Short, and R. Shomaker, Factors Affecting Fume Production 

in Surface Coal Blasting Operations. International Society of Explosives Engineers, 2002G, 

Volume 2, p. 307. 

10 Barnhart, CR, Understanding the “Orange Smoke” Problem in Cast Blasting. International 

Society of Explosives Engineers, 2003G, Volume 2, p. 307. 

11 Rowland JH, Mainiero, RJ [2000]. Factors affecting ANFO fumes production. In: Proceedings 

of the 26th Annual Conference on Explosives and Blasting Technique. Anaheim, CA: 

International Society of Explosives Engineers, pp. 163-174. 

12 Explosives and Rock Blasting, published by Atlas Powder Company, Field Technical 

Operations, 15301 Dallas Parkway, Colonnade Suite 1200, Dallas, TX 75248-4692, 1988, p 25. 

13 ISEE Blasters’ Handbook, Seventeenth Edition, International Society of Explosives Engineers, 

Cleveland, OH, 1998, p 48.