Dust-Off and similar products contain difluoroethane, trifluoroethane, or I believe tetrafluoroethane.
They share these aspects:
1. Everytime you inhale, you are basically playing a game of Russian Roulette, except the cause of death would be SSDS (Sudden Sniffing Death Syndrome) instead of a bullet to the head.
2. The high is very similar if not identical to the high from Nitrous Oxide, which is perfectly safe.
In other words, NEVER INHALE COMPUTER DUSTER AGAIN. GET A CRACKER, SOME WHIPPETS, AND SOME VITAMIN B-12 and have fun. SAFE fun.
EDIT: And to clarify, I do have experience. Years ago, I stupidly believed my friend when he (thinking he was right, but being in fact mistaken) told me the contents of computer duster was nitrous oxide. I used it at least a dozen or more times and had much fun. But I soon after read the labeling carefully, did research, and asked a pharmaceutical chemist with an IQ of 196 what the deal is with computer duster products, and the verdict is: DON'T DO IT, EVER.
There is only 1 safe inhalant. Nitrous. And being that it's the only safe inhaled drug, it's more commonly/accurately classified as an analgesic/psychedelic/dissociative.