You already have your rough geolocation leaked simply by using the mail system. This is more important for smugglers who use long series of runners, or multi-vehicle transportation. I have tried in the past to look for a formula to determine how fast given substances will permeate through various sorts of vac bags but I can't find anything, any physics people here want to help? It would really come in handy, if it only takes a day for the scent of MDMA to permeate through the vac bag a certain vendor is using it might not be such a hot idea to try importing through customs from them. I have asked people with physics backgrounds for help on this before but the best answer I could get out of them was "use vacuum sealed glass containers". Not sure if that is the best option for smuggling though .