Office of Mineral Resources Management
Tom Ridge, Governor
James M. Seif, Secretary
Mining and Reclamation Program Advisory
Number: 001 DATE: July 8, 1997
Subject: Carbon Monoxide Poisoning from Blasting Activities
To: Licensed Blasters
Roderick A. Fletcher, P.E.
Bureau of Mining and Reclamation
Bureau of District Mining Operations
Purpose: To make licensed blasters aware that carbon monoxide poisoning resulting from blasting activities could affect the health of nearby residents if precautions are not taken.
Background: Over the past few years, several incidents have occurred where individuals have become sickened from carbon monoxide gas produced from nearby construction and trench blasting.
Advisory: Individuals who conduct blasting must be aware that the detonation of explosives produces toxic gases. It is these gases that break and move the material being blasted.
Characteristically, the gases travel along the path of least resistance. In most cases, the blast creates a heave, or a free face is displaced. In either case, the gases can quickly escape into the atmosphere. In some unique situations, however, the gases will travel through the ground.
In recent years, there have been several instances of gases entering homes near trenching and construction blasting operations. Residents living in the homes were overcome by the gas, sickened and were rendered unconscious. Only quick actions by neighbors, or others residing in the home, averted catastrophic results.
A review of these incidents indicates that the gases traveled along buried utility lines, through the soil, or through naturally occurring fractures in the rock, and entered the homes at the foundation level. In all of these situations, the path of least resistance for the movement of the gases appears to have been in the direction of the homes. Little or no heave was created by the blasts nor was a free face displaced. In many cases an impervious clay or other confining layer covered the rock being blasted. In order to help confine the blast energy, this overlying material was not removed prior to blasting. In these cases the confinement was so great that most, or all of the gases remained in the ground. Each succeeding blast acted like a pump and pushed more gas into the fractures, which eventually entered the homes.
Recommendation for Action: When it is necessary to blast in close proximity to buildings, it is recommended that blasts be designed to allow for the gases to escape. This may be accomplished by blasting to a free face or creating a heave on the ground surface. If site conditions do not allow for this type of design, then venting of the gases by other means, such as vent holes, may be necessary. The important factor is to create an avenue to allow the escape of gases so that migration to buildings does not occur.
Please contact Mr. Rick Lamkie, Explosive and Safety Section, at (717)787-7846 with any questions.