Municipal Solid Waste (MSW) Landfill: virtual
tour
How Does Landfill Gas Move? How Does it Enter Buildings and Homes?
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How does landfill gas move?
 Once
gases are produced under the landfill surface, they generally move
away from the landfill. Gases tend to expand and fill the available
space, so that they move, or “migrate,” through the limited
pore spaces within the refuse and soils covering of thelandfill.
The natural tendency of landfill gases that are lighter than air,
such as methane, is to move upward, usually through the landfill
surface. Upward movement of landfill gas can be inhibited by densely
compacted waste or landfill cover material (e.g., by daily soil cover
and caps). When upward movement is inhibited, the gas tends to migrate
horizontally to other areas within the landfill or to areas outside
the landfill, where it can resume its upward path. Basically, the
gases follow the path of least resistance. Some gases, such as carbon
dioxide, are denser than air and will collect in subsurface areas,
such as utility corridors.
How does landfill gas enter buildings and homes?
 Gases
migrating from a landfill may eventually reach buildings and homes.
Foundation cracks and gaps, pressure differences between the inside
and outside of the building or home, mechanical ventilation systems,
and leakage areas (e.g., utility entry points, construction joints,
or floor drain systems) provides entry points for gases. Buildings
and houses with basements generally provide the easiest access
for gases migrating in the soil. The amount of gases let into a
building or home depends on a number of factors, including the
construction and maintenance practices. The gas concentration in
indoor air also depends on the building or home design, the rate
of air exchange, and the distance of the building or home from
the landfill.
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