What material does not retain a fumigant very well, even when well sealed?

Plastic is the material that does not retain a fumigant very well, even when it is well sealed. This is primarily due to its permeable nature. Plastics can have varying degrees of permeability based on their type and formulation, and many commonly used plastic materials allow fumigants to escape more easily than other materials like metal, wood, or concrete.

In contrast, metals are generally non-porous and create a solid barrier that can effectively contain gases, while concrete and wood, although porous, tend to hold fumigants more reliably than plastic under proper sealing conditions. This characteristic of plastics makes them less effective for storage or treatment purposes involving fumigants, emphasizing the importance of material selection in pest control practices where gas containment is critical.