Overview
Observations
- 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.
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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
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