Fumigation is currently a widely used method for rapid control of insect and mold diseases in cultural relics, but it also has problems such as weak desorption and easy secondary damage to cultural relics caused by residues. Focusing on three commonly used organic fumigants, this study has established a volatility detectionsystem based on the photo-ionization detection method. Using the Fick’s law, a prediction model for the volatilization rate of fumigants per unit area was established to accurately detect the residual amounts of fumigants. The results indicate that there was a good linear relationship between the mass fraction of organic fumigants and the sensor output value. The use of photo-particle sensors of the photo-ionization detector (PID) had good detection sensitivities for three organic fumigants—citronellal, citral and citronellol, with values of 2.072,1.287 and 0.702 V/(mg/L), respectively. The calculation results of the residue volatilization rate calculation model derived from the Fick’s law show that the correlation coefficient R² between the measured and predicted volatilization rates of the three organic fumigants was close to 1, and the significant difference P value approached 0. This model could be used accurately for the calculation of residue volatilization rates. In addition, it was found that under environmental conditions of 22℃, 60% (RH) and normal atmospheric pressure, and after complete fumigation of rice paper, the residual amounts of citral, citronellol and citronellal approached 0.1,0.06 and 0.01 ng/mm² after 5 hours of desorption, and all the residual amounts approached 0 ng/mm² after 72 hours of desorption. Therefore, the PID sensor and residue volatilization rate calculation model proposed by this study could accurately detect the residual amount and volatilization rate of fumigants used for paper cultural relics in practical applications, providing important new technical support and safety protection for the detection work for the fumigation and disinfection of paper cultural relics.