In this study, an attempt was made to measure uncertainties involved in the analysis of gaseous VOC standards prepared at various dilution stage. A GC/FlD system equipped with air server/thermal desorption (AS/TD) unit was used to draw calibration curves for the known amounts of VOC gases (including benzene, toluene, xylene, and styrene) prepared at four individual concentrations (10, 20, 50, and 100 ppb). The calibration curves obtained from standards of each respective concentration were compared with each other. It was found that the loss of samples was more prominent with decreasing standard concentrations (e.g., one prepared at 10 ppb) and that the heaviest compound, styrene exhibited the most noticeable loss than the others. In this study, an ancillary experiment was also conducted to evaluate the compatibility of standards between gaseous (using Tedlar bag) and liquid phases (using tube method). Based on this comparative analysis, the compatibility between two standard type was evaluated in terms of the recovery ratio between gas and liquid: 56 (benzene), 42 (toluene), 31 (p-xylene), and 25% (styrene).