Evaluating of the Effect of Sulfuryl Fluoride in Structural Fumigation of a Flour Mill
In this paper,integrated structural fumigation was conducted in the spaces in Area B and Area C of a flour mill in South China,108 m long,25 m wide and 35.2 m high,with a total volume of 95 040 m3 and an effec-tive fumigation volume of 53 842 m3,with a sulfuryl fluoride dosage of 40 g/m3 and a sealing time of 48 h.Under the condition of not supplementing sulfuryl fluoride fumigant,the daily loss rate of fumigant Ld and concentration half de-cay time HLT were established,the variation law of sulfuryl fluoride concentration on each floor and the leakage de-gree of fumigant were analyzed,and the insecticidal effect was evaluated.The results indicated that Ld of sulfur fluor-ide fumigants conformed to the model:Ld=100 ×(1-e-b)(e,natural constant;b,attenuation constant),HLT conformed to the model:HLT=ln2/b.The changes of daily loss rate of fumigant increased with the increase of attenua-tion constant,and the changes of HLT decreased with the increase of attenuation constant.When the attenuation con-stant was fixed for a single fumigation,the daily loss rate of fumigant and HLT were constant.According to the model evaluation,the daily loss rate Ld and half decay time of Floor 6,7 and 8 ranged from 56.7%to 71.3%and 0.56 to 0.83 d.The regional loss rate Ld and half decay time of Floor 3 and 4 ranged from 85.0%to 92.6%and 0.27 to 0.37 d,respectively.Except that the half decay time(HLT)of sulfuryl fluoride fumigant concentration on the 8th floor was more than 15 h,the other floors were not more than 15 h.After 22 d of fumigation,several live larvae of red flour beetles(Tribolium castaneum Herbst:Coleoptera:Tenebrionidae)were found in the equipment and pipes in large flour mills,and a small number of pupae of red flour beetles were found in the sampling process.Sulfuryl fluor-ide was used to fumigate the building structure with a dose of 40 g/m3 and a sealing time of 48 h can kill all insect states of pests in the workshop space area and adults in pipelines and equipment,and eggs existing in equipment and pipelines may survive and develop into new larvae or pupae.