OSHA Definition of a HNOC Clarified For The HCS

Stephanie McCauley

On March 4, 2014 OSHA released an open letter to the American Petroleum Institute clarifying how they interpret the Hazard Communication Standard (HCS) regarding Hazards Not Otherwise Classified (HNOC).


From the official definition, a HNOC is a negative physical or health effect that doesn’t fit the HCS categories.

A negative effect has to occur from workplace exposure to a chemical causing material health impairment or functioning. Employees must be free from negative effects even if regularly exposed to the chemical.

The criteria for classifying a negative health effect is the weight of evidence as described in Appendix A. All available information will be considered together using expert judgment. Also important is the quality of the data, with a precedence on good quality human data, routes of exposure, and positive and negative results.


If there is a physical or health hazard that fits the HCS category, but is less than the stated cut-off value or concentration it is not a HNOC.

Also categories of GHS Hazards not adopted by OSHA – like acute toxicity – are also not an HNOC.

Furthermore, OSHA considers “physical effect” in the definition to be impairment of health or function caused by a chemical’s hazards in normal conditions or foreseeable emergencies. This means scalds by an exposure to chemicals at high temperature or slipping on a spilled liquid chemical does not make those hazards a HNOC.

For example, OSHA does not consider water a HNOC because an employee may be scalded by boiling water, get hypothermia from being in cold water, slip in a puddle, or be knocked down by water sprayed at high pressure.

A HNOC is also not a pyrophoric gas, simple asphyxiate or combustible dust because they have intentionally been added to the “hazard chemical” definition.

HNOC Labelling Requirements

There are no Safety Data Sheet (SDS) label requirements for a HNOC, and such information does not have to be physically separate, but must not cause confusion with the required information.

On the label, the only two signal words that may be used are “danger” and “warning” and the correct signal word for a HNOC must be used.

Because a HNOC is determined through the hazard classification process, that information can be included under the required sections.

2014 Interpretations

In addition to creating new and updating current regulations, OSHA publishes interpretations and answers to questions about existing rules. Here is what has been released in 2014:

  • Construction’s Electrical Power Regulations Final Rule
  • Cranes and Derricks Near Power Lines
  • Recordkeeping for Multiple Business Establishments
  • How to Decide It’s a Workplace Injury
  • Safety Data Sheet (SDS) Reporting of Petroleum Streams
  • Combustible Dust Labeling Requirements in Hazard Communication Standard (HCS)
  • OSHA Definition of A HNOC Clarified for the HCS
  • General Duty Clause Covers All Impalement Hazards
  • Employer Responsible for Determining Qualified Rigger Status
  1. Next Post:
  2. Previous Post:

Get In Touch