We investigated the probability of measuring the odor of thirdhand smoke using four odor-measuring monitors and three gas detector tubes. We measured the changes in tobacco odor on paper towels and cloth products over time. The results of the measurements were plotted against time to obtain an exponential approximation curve. The coefficient of x and the R2 values were calculated from this curve. The odor indicated by four types of odor-measuring monitors and three types of gas detector tubes decreased exponentially over time. The curves obtained from all measuring devices had coefficients of ex between -0.001 and -0.021, and R2 values of >0.8. The reproducibility of measuring relative odor levels through all measuring devices was high, suggesting a good capability of measuring thirdhand smoke odor. Two different odor-level standard gases can be used for the calibration of the regression curve for each monitor.
