If several kilos of cocaine are put inside a welded titanium box, can drug sniffing dogs still detect it? what?

will drug sniffing dogs not be able to detect regardless of how good they are? what type of metal will drug sniffing dogs not be able to through, titanium, alloy, copper, bronze, ect...? what can fool them? what would throw them off? are drug sniffing dogs essentially perfect? what will they not be able to detect if they are that good? does anyone know where their achilles heel will be? RSVP. THANKS FOR ANY SUGGESTIONS.