There is a thread re some dudes who do tests with different packaging methods then use a real drug dog to see if it can detect anything, normal val seal does virtually fuck all to protect against canine detection, they found cocaine permeated one layer in 15 minutes so hardly effective. Given how stinky weed is you need to be using a non permeable heat sealed layer to avoid it being detectable by dogs. Do a search for the thread, it's a good read.