Environmental

In Montana, 'vapor intrusion' is a pathway by which contaminated groundwater or soil contamination can affect indoor air quality when:

AWater vapor from humidifiers accumulates indoors

BVolatile chemicals from subsurface contamination migrate upward through soil as vapors and enter buildings through foundation cracks and openings✓ Correct

COutdoor air quality index exceeds EPA standards

DHVAC systems draw in contaminated outside air

Explanation

Vapor intrusion occurs when volatile chemicals (chlorinated solvents, petroleum hydrocarbons) from contaminated soil or groundwater vaporize and migrate upward into overlying buildings, potentially creating hazardous indoor air concentrations.

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