Freight Containers——Are They Sufficiently Gastight for Quarantine Preshipment Fumigation with Methyl Bromide in the 21st Century?

摘要

Freight containers are used to transport virtually all non-bulk cargoes traded internationally, with a considerable proportion of this freight still subject to quarantine or preshipment fumigation with methyl bromide. Most of these fumigations are carried out under sheets. Some quarantine and other authorities allow fumigations to be carried out directly in the container,without sheeting or harping, often with additional restrictions to ensure success of the treatments. Restrictions include specifying minimum levels of sealing or gastightness, such as measured by pressure test, or use of particular kinds of containers only, e. g. reefers. Where a container can be demonstrated to be gastight by pressure testing,it may be used directly as a' chamber' or gastight enclosure. This paper presents a summary of the mathematical background to pressure testing, information relating to gas loss from freight containers, and some practical observations on fumigant retention at different pressure test values. Both the theory and limited practical studies available support a minimumpressure test specification of 10 seconds pressure half life for containers to be used directly as enclosures, without sheeting. This applies to the container in the filling condition to be treated. Below this level of sealing, risk of fumigation failure increases.