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  • It is rarely beneficial to score the air pathway in areas of low population density.
  • Due to distance-weighting, the air pathway score is frequently very low in the absence of an observed release.
  • Determining an air pathway score is straightforward, particularly as an adjunct to scoring the soil exposure pathway.
  • Data from health and safety sampling can frequently be used to:
    • support an observed release through direct observation
    • provide evidence of biogas release

Outdoor Air Restriction

  • The air pathway addresses releases to the outside atmosphere only.
  • Indoor air contamination data can be used to support an outside observed release by chemical analysis.
  • Indoor air contamination cannot be scored using the air pathway except in terms of its potential to escape into the outside air.
  • Buildings containing indoor air contamination located on a site can be considered sources in certain circumstances. Consultation with EPA is necessary in such circumstances.
  • Interstitial air spaces in soil is not considered to be part of the outside atmosphere.

Gaseous and Particulate Substances

  • Distinguish between gaseous substances (vapor pressure greater than or equal to 10-9 torr) and particulate substances (vapor pressure less than or equal to 10-1 torr).

Highlight 10-2
Vapor Pressure Ranges for Gaseous and/or Particulate Hazardous Substances

slide 16.10

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