Washington State University
Environmental Health & Safety GHS Hazard Classification

Hazard Classification

Chemical manufacturers and importers have responsibility for hazard classification. WSU employers are not required to classify chemicals. The following hazard criteria have been developed in the new GHS aligned Hazard Communication Standard (HCS).
Physical Hazard Criteria

  • Explosives
  • Flammable Gases
  • Flammable Aerosols
  • Oxidizing Gases
  • Gases Under Pressure (comprised of compressed gases, liquefied gases, refrigerated liquefied gases, and dissolved gases)
  • Flammable Liquids
  • Flammable Solids
  • Self-Reactive Chemicals
  • Pyrophoric Liquids
  • Pyrophoric Solids
  • Self-Heating Chemicals
  • Chemicals which, in contact with water, emit flammable gases
  • Oxidizing Liquids
  • Oxidizing Solids
  • Organic Peroxides
  • Corrosive to Metals
  • Combustible Dusts (*OSHA defined hazard; not part of GHS)
  • Pyrophoric Gases (*OSHA defined hazard; not part of GHS)

Health Hazard Criteria

  • Acute Toxicity
  • Skin Corrosion/Irritation
  • Serious Eye Damage/Eye Irritation
  • Respiratory or Skin Sensitization
  • Germ Cell Mutagenicity
  • Carcinogenicity
  • Reproductive Toxicity
  • Specific Target Organ Toxicity – Single Exposure
  • Specific Target Organ Toxicity – Repeated Exposure
  • Aspiration Toxicity
  • Simple Asphixiants (*OSHA defined hazard; not part of GHS)

Environmental Hazard Criteria (*Not regulated by DOSH or OSHA)

  • Acute Aquatic Toxicity
  • Chronic Aquatic Toxicity (includes bioaccumulation potential and rapid degradability)

Hazard Not Otherwise Classified (HNOC) means an adverse physical or health effect identified through evaluation of scientific evidence during the classification process that does not meet the specified criteria for the physical and health hazard classes addressed in the Hazard Communication Standard (HCS). This does not extend coverage to adverse physical and health effects for which there is a hazard class addressed in the HCS, but the effect either falls below the cut-off value/concentration limit of the hazard class or is under a GHS category that has not been adopted by OSHA (e.g. acute toxicity Category 5).


OSHA Quick Card: NFPA 704 and HazCom 2012 Labels

Hazard Category Number System

The GHS aligned HCS introduces a hazard category number system to classify the hazard levels within the different hazard criteria (above) to determine what label information is required. The purpose of the number system is to inform workers about the hazards of chemicals in the workplace under normal conditions of use and foreseeable emergencies.
This hazard category number system classifies hazards on a scale from 1 to 4, with 1 being the most severe hazard and 4 being the least severe hazard. There is no 0 category. These hazard category numbers are NOT required on labels but are required on Safety Data Sheets (SDS).

The HCS number system should not be confused with the National Fire Protection Association (NFPA) 704 Number System. The NFPA system uses a multi-colored diamond and numbers to represent flammability, health, reactivity and other special hazards on a scale of 0 to 4, with 0 being the least hazardous and 4 being the most hazardous. The purpose of this system is to provide basic information for emergency personnel responding to a fire or spill and those planning for emergency response. 
It is crucial that personnel working around hazardous chemicals understand the differences between these two number systems and when and why they are used. The HCS number system is required by law to classify hazards and to be placed on SDSs in section 2 to communicate those hazards. The NFPA system is not required by law to be on chemical labels or SDSs. Before the new HCS, the NFPA system was often used because it was the best system developed at the time and it was widely accepted as a means to communicate basic hazard information, especially to emergency personnel. More importantly, the NFPA system is referenced in building fire code laws.

It should also be noted that the two systems are not interchangeable. The hazard category numbers found in section 2 of a HCS compliant SDS are NOT to be used to fill in the NFPA 704 diamond. Similarly, it should not be assumed that a 1 under the HCS system equals a 4 under the NFPA system as that is not the case. Lastly, the NFPA system will still be in use for other applications, such as signage on buildings containing hazardous chemicals. You may even see it in the last section of a SDS, titled “Other Information”.

For a summary of the two number systems on a printable PDF document, please click on the “OSHA Quick Card” link under Resources of this page.