1. A passive kinetic sampler for quantitative passive soil vapor concentration measurement comprising: a container filled with a sorbent medium; wherein selected sampler dimensions constrain the uptake rate to match values that minimize or eliminate a starvation effect as calculated via mathematical models; wherein the mathematical models calculate the diffusive delivery rate of vapors to a void space in which a passive sampler is deployed and depend at least in part on soil moisture and porosity; and wherein the uptake rate, as constrained by the selected sampler dimensions, is less than or about the delivery rate of vapors from surrounding soil, so the concentration of vapors in the void space within which the sampler is exposed is similar to the concentration in the surrounding soil gas throughout the majority of the sampling interval.