Compressed Gas: Classification of Hazard
Use and storage of compressed gases is strictly regulated according to hazard classification. See the Toxic and Hazardous Gas Classifications Chart to identify the hazard class of a particular gas.
Compressed gases are classified as class 1, 2, 3 and 4, with 4 being the highest hazard. Classes are based on the lethal concentration to 50% of test animals (rats) of each gas (LC50). Once you define the Classification of Hazard, view the Requirement Matrix.
| Compressed Gas Health Hazard | Description | Criteria |
|---|---|---|
| 4 | Gas that under emergency conditions will be lethal. | LC 50 for inhalation is less than or equal to 1000 ppm; Flammable gases; flammable cryogenic materials; any liquid or gaseous material that is liquid while under pressure and has a flash point below 22.8 C (73 F) and a boiling point below 37.8 C (100 F); materials that ignites spontaneously when exposed to air. |
| 3 | Gas that under emergency conditions will cause serious or permanent injury. | LC 50 for inhalation is greater than 1000 ppm but less than or equal to 3000 ppm; cryogenic gas that can cause frostbite and irreversible tissue damage; compressed liquefied gases with boiling points at or below -55 C (-66.5 F) that cause frostbite and irreversible tissue damage. |
| 2 | Gas that under emergency conditions will cause temporary incapacitation or residual injury. | LC 50 for inhalation is greater than 3000 ppm but less than or equal to 5000 ppm; compressed liquefied gases with boiling points at or below -30 C (-22 F) and -55 C (66.5 F) that cause severe tissue damage, depending on length of exposure. |
| 1 | Gas that under emergency conditions will cause significant irritation. | LC 50 for inhalation is greater than 5000 ppm but less than or equal to 10,000 ppm. |