Investigators examined the effect of this decay in some preliminary calculations and determined that decay would be insignificant. Investigators believe these rates to be reasonable given reports that strong winds readily penetrated the structures under consideration. Furthermore, investigators believe these air exchange rates to be representative for tents used during deployment in a hot, potentially windy environment, where flaps might frequently be open. The box model equations were used to estimate equilibrium concentrations and average concentrations over the first 16 hours of exposure following the installation of the resin strip. The estimated equilibrium concentrations of dichlorvos in the tent are listed in Table 52.
Concentrations start at zero and rapidly approach the corresponding equilibrium concentrations.
Table 53 presents a summary of the calculation of estimated concentrations. Three of these methods were based on dichlorvos air concentrations measured in homes using pest strips in a 1973 study. EPA's fourth method is most similar to the approach used in this analysis. The 1973 indoor air measurement study used as the basis for three of EPA's exposure estimation methods showed lower dichlorvos air concentrations than those estimated with the models discussed above. This is comparable to the concentrations estimated here for the low and medium exposure scenarios.