When does landfill gas pose an explosion hazard?
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 (see Chapter Two, “What factors affect landfill gas migration?”). Gas collection and treatment systems, if operating properly, reduce the amount of gas that is able to escape from the landfill. (See Chapter Five.) • 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), as defined at right. Lower and Upper Expl
