Non-porous materials

Do you know of any completly, or highly non-porus materials?

I was wondering about how sniffer dogs can smell drugs through plastics, and have heard through "Berry Cooper's Never Get Busted Again" DVD, thats dogs smell through seemingly "impossible" things because of the porousity of the materials. I've also heard that moleclues will go through ANY THING given enough time. Wether this is all true or not I don't know, as I study math.

Is there anything more sutible for wrapping drugs than plastic?

>I've also heard that moleclues will go through ANY THING given enough time.

If the molecules are small enough, they will pass through the pores.  That is what determines whether or not diffusion occurs.

A metal container would stop any volatile compounds from escaping.