Confined Space Hazard Classification System

The Department of Transportation (DOT) lists hazardous chemicals within nine classes in the Emergency Response Guidebook put out by the Pipeline Hazardous Materials Safety Administration (PHMSA). OSHA follows this codified system when dealing with chemical hazards within confined spaces. As an authorized entrant, you must be aware of these hazards.

The nine hazard classes are:

• Class 1 - Explosives
• Class 2 - Gases
• Class 3 - Flammable liquids
• Class 4 - Flammable solids; substances liable to spontaneous combustion; substances which, in contact with water, emit flammable gases
• Class 5 - Oxidizing substances and organic peroxides
• Class 6 - Toxic and infectious substances
• Class 7 - Radioactive material
• Class 8 - Corrosives
• Class 9 - Miscellaneous dangerous goods

Please note that the class numbers are for convenience only; they DO NOT indicate a relative degree of danger. You may or may not encounter these hazards in a confined space; it is useful to be aware of them anyways.

To learn more visit our Confined Space Online Training web page.