A novel method for pre-ventilation of shipping containers

摘要

Numerous shipping containers arrive with high levels of hazardous volatile chemicals in the interior air. This may constitute a health risk during inspection and unstuffing. The problem remains largely unaddressed due to ignorance, lack of suitable field instruments for chemical identification, and lack of easy to use, effective ventilation methods. Here, we present a novel ventilation approach based on extraction of air from the closed container via the existing top corner ventilators. A suction plate was developed to fit tightly over the corner ventilator and connected with a flexible hose to an extraction fan. Air flow rates and vacuum under the plate were measured in the lab with five different types of extraction fans. The vacuum produced under the suction plate held it securely in place. Washout of air contaminants under different configurations and ventilation scenarios was studied in an experimental 20-ft container stuffed with acetone emitting cardboard boxes and in the field with containers stuffed with commercial goods. Volatiles in container air were continuously recorded with logging photoionization detectors in various positions before, during and after ventilation. A maximum air flow through the ventilator of 186 m(3)/h was achieved. At 100 m3/h, the initial acetone levels were reduced to 11% and 4.9% in the tightly stuffed and to 6.0% and 3.1% in the loosely stuffed (pallets) experimental container after 1 h and 4 h, respectively, as measured inside the closed door (mean values). As expected, the washout was somewhat slower in nine 40-ft field containers and reached 22% and 11%, respectively. In both experimental and field containers the concentration rose quickly when ventilation ceased. In conclusion, the new ventilation method allows for convenient, safe and efficient ventilation of risk containers. The container should be continuously ventilated until it is opened, or rapid re-accumulation of volatiles will occur.