Posted this somewhere in response to TGT topics but thought I'd put it up here for more to see as it's discussed a lot and to put minds at ease when people recieve packages without a vac pack.
I've seen a lot of mention about vacuum packing and feel the need to address something:
If you have a thermos, for example, two solid walls of glass are parted by a void that contains vacuum pressure. The glass resists the forces due to it's solid state and thus keeps this vacuum space between, without being pulled together by it. This removes any medium, such as air, from being able to transfer heat from inside the thermos to the outside air and keeps it warm. You also cannot smell through the vacuum for the same reason. No medium for particles to interact
And here lies the confusion.
Now, when you vac pack a plastic bag you are simply removing a lot, but not all, of the air from the packet. This serves to preserve freshness or decrease something's size like bedding and pillows, for example but nothing more. The imperfect "vacuum" that you create here contains the weed in itself. What is preventing the smell from escaping is nothing more than the non-porous package and it's heat seal. The coffee in the thermos is not in a vacuum, the vacuum is between the vessel and the outside air.
Unless the weed is packaged in a solid airtight container, inside a larger airtight container, with a vacuum BETWEEN those two containers, then the vac pack will not serve to hold the smell. That's why the smell-proof mylar bags are used and heat sealed. THEY are what keeps the smell at bay.
I welcome anyone with a vacuum sealer to experiment. Wrap two identical packages, vacuum one and not the other, put in mylar bags and heat seal. I can assure you, you will find no difference in smell.