The physical properties of most sensory stimuli are well understood and can be precisely controlled. In contrast, olfactory stimuli are frequently composed of a myriad of different volatile chemicals that differ in their chemical structure, volatility, how they adhere to surfaces, and interact with other chemicals in both the liquid and gaseous phases. To simplify these issues, most olfactory studies rely on the presentation of monomolecular odorants under standard environmental conditions. While this approach allows odor identity to be precisely manipulated, controlling the concentration and kinetics of the odor pulse is still a major challenge. An easy and affordable method to estimate vapor concentration would increase the transference of experimental data across laboratories and allow odorants to be presented at equivalent standardized concentrations. Our approach uses a photoionization detector and simplified olfactometer setup to assess the relationship between the liquid and vapor-phase concentrations of odorant/solvent pairs. The resulting equilibrium equations successfully correct for behavioral sensitivity differences observed in mice tested with the same odorant in different solvents and were overall similar to published measurements using a gas chromatography-based approach. Although these results take an important step towards the creation of a practical archive for vapor-phase odorant quantification, they do not help constrain the relevant range of odorant concentrations that should be used in functional studies. To help address this issue, we have defined the minimum relevant concentration for a variety of structurally diverse odorants using our behavioral thresholding approach in mice. It is our hope that these liquid-/vapor-phase equilibrium equations and behavioral thresholds will allow researchers to appropriately choose stimulus intensities for functional studies in a manner that will allow more accurate comparisons across laboratories.