Computer duster is a completely different thing. Common duster gases include hydrocarbon alkanes, like butane, propane, and isobutane, and fluorocarbons like 1,1-difluoroethane, 1,1,1-trifluoroethane, or 1,1,1,2-tetrafluoroethane. All extremely dangerous.

Nitrous oxide ("laughing gas" or "whip-its") is what the dentist gives you. Fairly harmless unless used for prolonged periods, or if used in such a way that you are being deprived of oxygen.
In stores it commonly has delicious whipped cream added to it to encourage people to consume it. These also require food-grade nitrous oxide, and contain no other chemicals for FDA safety reasons.