An engineered membrane installed beneath a building slab or foundation to block intrusion of volatile organic vapours from contaminated soil or groundwater into indoor air. Typical materials include HDPE, EVOH co-extrusions, and spray-applied asphaltic systems with chemically resistant seams.
Vapour barriers are the passive component of vapour intrusion mitigation, sized and detailed against the specific chemistry on site. For chlorinated solvent and petroleum plumes, conventional 6-mil polyethylene is inadequate; site-specific systems use multi-layer EVOH-cored membranes that resist permeation by TCE, PCE, benzene, and naphthalene. Seam quality and penetration detailing (utility chases, plumbing) typically determine performance more than membrane material.
Where source-zone destruction is feasible, vapour barriers are best treated as belt-and-suspenders rather than primary remedy: they impose a long-term inspection and reseal obligation on the owner, and any future renovation that penetrates the slab can void protection. Code-mandated installation in known vapour-intrusion zones, combined with sub-slab depressurization, is the current best practice.
Also known as: vapour barrier, vapor barrier, VI barrier, sub-slab membrane.
Vapor Intrusion: treatment approach
The subsurface-to-indoor-air migration pathway for volatile contaminants. It is investigated with sub-slab and indoor-air sampling and mitigated primarily by sub-slab depressurization systems that reverse the pressure gradient driving vapor into the building.
An ex-situ soil treatment process that heats contaminated soil to volatilize and separate organic contaminants from the soil matrix, after which the liberated vapors are captured and treated, usually in a high-temperature oxidizer.
A thermal desorption configuration where the heat source contacts the soil directly inside the rotary unit, delivering high heat-transfer efficiency and supporting higher treatment temperatures.
A thermal desorption configuration where heat is conducted through the wall of the treatment vessel without combustion gases contacting the soil, producing a concentrated, lower-volume vapor stream suitable for condensation and recovery.
Treatment that heats contaminated soil and groundwater in place, typically with electrical resistance, thermal conduction, or steam injection, to volatilize and recover contaminants without excavation. Used where excavation is impractical or where the contaminant zone sits beneath active infrastructure.