Miller Magazine Issue: 131 November 2020

55 COVER STORY MILLER / November 2020 transformative effects of ‘Industry 4.0’ through the use of smart digital devices and data management tools, we hereby recommend a similar paradigm shift for the busi- ness sector of commodity and food pest management. Leakage Almost every storage structure is leaking. Differences in day-night temperatures create internal currents and pressure that increase leakage. A windy day will also dra- matically increase fumigant losses. Leakage is expected through the silo roof and silo base, through non-air-tight silo valves, through container doors with aged sealing, through container floors, through ship hold covers with aged sealing, through plastic covers of improper thick- ness in stack fumigations, through doors and windows, through panel connections or brick walls, through railcar walls, through tarpaulin punctures and floor cracks. See Figure 1 for illustration. A silo is truly sealed if it passes a five-minute half-life pressure test, for instance according to the Australian Standard AS2628. This is a good method to determine the level of tightness of a structure before applying fu- migant. The use of measuring equipment will validate the good sealing. Wireless fumigant sensors that can be placed inside the fumigated volume, such as those avail- able by Centaur, are the best tool for monitoring phos- phine, CO 2 or low O 2 treatments. Phosphine fluctuation Fumigator perception used to be that product tem- perature is important only to determine which fumiga- tion protocol can be applied. For example, the Coresta protocol requires 200 ppm for 4 days when temperature is above 20 degC and 300 ppm for 6 days when tempera- ture is between 16-20 degC. A relatively new discovery is that phosphine concentration fluctuates constantly, fol- lowing temperature fluctuations in the storage area and Figure 1: Left graph shows a well-sealed chamber with a concentration drop of only 171ppm in 2 days. Right graph shows a poorly sealed warehouse with a dramatic drop of 1242ppm in 2 days. Figure 2: Phopshine concentration dropping when temperature is above 20 degC, in a stack fumigation.