"Duster" is Compressed Gas - you know, it comes in a can to spray on hard-to-reach spots in electronics, such as keyboards, circuits, moving parts, etc.

It is EXTREMELY dangerous to use as a drug, and can easily be fatal.

Since there is so much bad drug information out there, SNOPES has shown that one story, about the death of the teenage son of a Police Officer, written by the officer himself, is true.
http://www.snopes.com/medical/toxins/dustoff.asp

If someone cannot find something safe, like weed, I'd advise having some wine, beer or even hard liquor - as long as you do it responsibly and in moderation. Taking the risk of killing yourself, or getting brain damage, with duster, or other deadly inhalants, is just plain stupid.