California Department of Pesticide Regulation (CDPR) monitored sulfuryl fluoride (SO2F2) indoor concentrations of twenty-three structural fumigations of residential houses in eight counties between September 2014 and March 2015. We placed Remote Data Acquisition (RDA) Fumiscopes® at the center of the fumigated houses and RDA Fumiscopes® measured the SO2F2 indoor concentration from four locations of the houses once very hour. Assuming that the decreasing indoor SO2F2 was completely emitted to the outdoor environment, we used the monitoring data to estimate SO2F2 emissions during fumigation treatment and aeration periods. The results showed considerable variability of half loss time (11 – 60 hr) and mass loss (22 – 81%) during the treatment period. Due to the complexity and differences in residential structures, it is challenging to accurately estimate the fumigation volume prior to the application. Actual application rates for the same pest treatment also differed from house to house. Tarp and seal quality could be the most impactful factors for the mass loss of this period; however, they cannot be quantified. The decline of indoor concentrations followed the first-order kinetics. Therefore we were able to develop a model to calculate the hourly flux (g/m2s) of a treatment period using the following variables: initial concentration, treatment period mass loss, and house height. Although California Aeration Plan requires a minimum 12-24 hours of aeration after a treatment, our monitoring data showed that 93±5% of the mass at the end of treatment period was emitted through the ducting system within the first 2 hours. The ratio of the loss amount in the first hour to the loss in the second was 6:1 on average.

Estimating sulfuryl fluoride emissions during structural fumigation of residential houses

256th National Meeting (2018)

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