Municipal Solid Waste (MSW) Landfill: virtual
tour
Landfill Gas Safety and Health Issues
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 Explosion Hazard
Landfill gas may form an explosive mixture when
it combines with air in certain proportions. The following conditions
must be met for landfill gas to pose an explosion hazard:
- Gas production. A landfill must be producing gas, and this gas
must contain chemicals that are present at explosive levels.
- Gas migration. The gas must be able to migrate from the landfill.
Underground pipes or natural subsurface geology may provide migration
pathways for landfill gas. Gas collection and treatment systems,
if operating properly, reduce the amount of gas that is able to
escape from the landfill.
- Gas collection in a confined space. The gas must collect in a confined
space to a concentration at which it could potentially explode.
A confined space might be a manhole, a subsurface space, a utility
room in a home, or a basement. The concentration at which a gas
has the potential to explode is defined in terms of its lower and
upper explosive limits (LEL and UEL).
 Asphyxiation Hazards
Landfill gas poses an asphyxiation hazard
only if it collects in an enclosed space (e.g., a basement or utility
corridor) at concentrations high enough to displace existing air
and create an oxygen-deficient environment. The Occupational Safety
and Health Administration (OSHA) defines an oxygen-deficient environment
as one that has less than 19.5% oxygen by volume. Ambient air contains
approximately 21% oxygen by volume.
Carbon dioxide, which comprises 40% to 60% of landfill gas, may
pose specific asphyxiation hazard concerns. Because it is denser
than air, carbon dioxide that has escaped from a landfill and collected
in a confined space, such as a basement or an underground utility
corridor, may remain in the area for hours or days after the area
has been opened to the air (e.g., after a manhole cover has been
removed or a basement door opened).
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