Soil vapor surveys can be used for a number of purposes, including initial site screening, site assessment/characterization, risk assessments, remediation & post-remediation monitoring and ongoing monitoring. Three principal methods exist for collecting soil vapor data: active, passive, and flux chambers. The active approach consists of the withdrawal of an aliquot of soil vapor from he subsurface, typically with a sampling probe, followed by analysis of the withdrawn vapor. The passive approach consists of the emplacement of an adsorbent into the subsurface and subsequent removal and analysis of the adsorbent. Flux chambers consist of an enclosed chamber that is placed on the surface for a specific period of time.