I was reading an old post, and read about the idea of blowgun darts being traced back to you by your DNA. After a little thought I think I have found a solution; a filter, inside the mouthpiece, that would filter out any saliva that may contain any of your cells. Any resulting moisture would simply be evaporated water condensing on the dart or barrel.
I am pretty sure that such a filter would work, because they have filters that are like a shield that will block out harmful viruses from your breath when you give someone CPR. I think such a filter would be pretty easy to make, a few layers of panty hose would block any little bits of saliva from going into the blowgun barrel.
To use, you'd take of the mouthpiece, insert the dart (with gloves), replace the mouthpiece, and when you fire no DNA is left on the dart.

(Surely that would slow airflow down a considerable amount, rendering the blowpipe useless! I've approved this post to see if anybody has any other suggestions - kingspaz)

This might sound kinda stupid and void the whole concept of the blow gun....but my idea of a non tracable blowdart would be usiing a samll painball gun c02 tank. Not the cartriges but the really small tanks they seell at the sports store. It would give you more force then a puff of air and avoid any traces.

This might be awkward however when I read this thread an idea come to my mind.

AFAIK, the blowgun used by Ninjas may be a solution for this. These guns have an additional moutpiece which is almost perpendicular to barrel of the blowgun. IIRC I read somewhere they use this geometry in order to prevent themselves to breath in the dart accidentally. Maybe a longer side mouthpiece may prove effective in preventing saliva from getting on the dart.

What if you just covered the darts with H2O2 or something to destroy any deposited DNA

How about stuffing in a piece of light plastic bag just after the dart? It would press against the back of the dart when fired, when the dart leaves the barrel, plastic bag would just drop out and blend in with other garbage laying on the ground.

I doubt that anyone is ever going to kill someone efficently with blowgun anyway, but who knows...

The amount of spit can be incredible, especially if you fire several times in one session. I've observed cold spit collectin all over the dart, and even the target.

I don't think a filter is a good idea, because I can't imagine a practical way to filter without reducing effectiveness, which is supremely important since blow guns in general are short range.

If it were me, I'd use the wad (plastic bag?), but make sure not to leave it in the garbage, I once read about a (very) old crime when guns were just becoming popular, they identified the murderer by the wad left by his gun.

What if you just covered the darts with H2O2 or something to destroy any deposited DNA
I was thinking of the very same thing but with a different substance. IMHO alkali hydroxides are more suitable for this purpose. However, it is a problem to cover a dart with a caustic substance (to keep it for a long period of time of course). However, it might be possible to dip it in a caustic slurry /paste just before using it.

But that's also silly. Assume that you are carrying a container (it must be fairly high/long to receive entire length of dart) containing sodium/potassium hydroxide slurry/paste. :confused:
Maybe it's possible to oil the dart and powder it finely powdered KOH just before using.

I would go with co2 , infact most online blow gun stores sell adapters for blowguns that take co2 cartridges and you just squeeze the handle and it lets out a burst of air, you could probably get longer ranges with that also instead of blowing with your mouth