As I had no "proper" Air Duster, but plenty of butane refills I made one into a (slightly hazardous) Air Duster.
Parts required :
A metal tube from a portable TV aerial (the one I picked had a slightly rounded tip and probably resulted in higher speed airflow)
Plastic barbed "T" piece as used in garden watering systems.
Some silicone tubing, size to fit snugly inside the T-piece.
A small stopper (I used a cup-hook and silastic to seal it while screwing in.
A small metal washer with hole just the right size.
Step 1: Assembly Details
It's critical that the butane filler have a step in the filling tube, to stop the filling tube being pushed into the T-piece. If it doesn't, you will need a different type. The washer has to sit on this step.
If you pick the exit tube to be the same size as the butane filler tip, you only need one size of silicone tubing.
Assembly is pretty simple; just push all the bits together, holding a finger over the exit nozzle to reduce gas loss.
Note that in the picture above, I have pulled the exit tube and the filler tubes out from the T-piece a little for clarity.
I couldn't find how to add notes onto the pictures but I'm sure someone will tell me. Thanks in advance.
To use it, hold in one hand and depress the top of the T-piece. As a bonus, you can have instant freeze just by using it inverted.
DON'T FORGET IT IS INFLAMMABLE, SO BEST USED OUTDOORS OR IN A VENTILATED AREA WITH NO FLAMES NEARBY.
I used mine just now to blow fluff from my computer mouse.