SIMULATING THE EFFECT OF WEATHER CONDITIONS ON STRUCTURAL FUMIGATION

Estimating the half-loss time (HLT) is one of the most difficult tasks for fumigators. Fumigators assume no variation in weather conditions and rely on concentration readings from past fumigations when estimating the HLT value for a particular structure. Most of the time, fumigant overdosing is the approach taken to reduce the chance of a fumigation failure due to inaccurate HLT estimation. This results in excessive fumigant use and unnecessarily increases cost. Due to the substantial fumigation-to-fumigation variation, producing experimental replicates, in which certain parameters of interest are varied and all the other parameters are kept unchanged, is costly and almost impossible to implement. The primary objective of this study was to utilize the validated CFD models developed by Chayaprasert et al. (2006b) to evaluate the effect of multi-year weather conditions on the gas leakage rate (i.e., HLT) and the concentration×time (Ct) product during structural fumigation in a reference flour mill. Eleven fumigation simulations were performed using historical weather data of the same time period between 1996 and 2006. It was assumed that for each year’s simulation (1996 – 2006) the fumigation started at 12:00pm on the 4th of July and lasted 24 hours. Hourly average historical weather dat