Vapor intrusion

Vapor intrusion is the pathway by which volatile contamination in soil or groundwater migrates upward into buildings as indoor air — the mechanism that makes a plume under a lot a habitability question rather than an abstract subsurface fact. Chlorinated solvents from old dry cleaners and industrial degreasers are the classic sources; the pathway is studied with sub-slab and indoor sampling, and managed with mitigation systems resembling radon controls.

Vapor concerns drive modern environmental practice around historic commercial corridors: the corner dry cleaner's legacy reaches neighboring lots through the ground. In records, vapor questions surface via spill files, cleanup-program documents, and (E) designations for hazardous materials — and mitigation systems, once installed, are operating obligations that convey with the building.