As you can imagine, working with gas cylinders presents plenty of hazards: flammability, reactivity, toxicity, and asphyxiation. Mishandling can lead to explosions or more innocuous dangers...
Gases that corrode the material or tissue they come in contact with are classified as corrosive. They can also be reactive and toxic and/or flammable or an oxidizer. Most are hazardous in low concentrations over long periods of time.