Understanding New Hazard Classifications in WHMIS 2015: Part 2

In this installment of our WHMIS 2015 info series, we will continue our introduction to new hazard classifications. In part one of this article, we discussed biohazardous infectious materials and combustible dust. In part two, we will introduce you to asphyxiants and pyrophoric gases.


Simple asphyxiants and pyrophoric gases are new hazard classifications included in the Hazardous Product Act and Hazardous Product Regulations, but these are not hazard classes under GHS; these classifications are unique to WHMIS 2015 and OSHA HCS 2012.


What are they?

Simple Asphyxiants, as they are classified in WHMIS 2015, include any substance – gas or vapour – which has the potential to displace oxygen and rapidly cause suffocation. Typically, this occurs only when the material is in high concentration, as they usually have no physiological effects in low concentration. Simple asphyxiants often have few or no warning properties.  

Examples of simple asphyxiants include:

  • Hydrogen
  • Helium
  • Ethane
  • Ethylene
  • Nitrogen
  • Neon
  • Carbon dioxide
  • Acetylene
  • Argon
  • Methane
  • Propane
  • Propylene


Simple asphyxiants fall under the “physical hazard” class of WHMIS 2015 and are category 1 – the most severe level of hazard.

Warnings and Symbols

Simple asphyxiants are not identified by any WHMIS or GHS pictogram, but are identified with the signal word “warning” and the hazard statement “May displace oxygen and cause rapid suffocation.”

Pyrophoric Gases

What are they?

Pyrophoric gases, as defined by WHMIS 2015, include any substance – gas or vapor – which may catch fire spontaneously if exposed to air at a temperature of 130 degrees F (54 degrees C) or below. Pyrophoric gases must be stored in compressed gas cylinders. GHS Revision 6 has now adopted Pyrophoric Gas as an official GHS classification.

Examples of common pyrophoric gases include:

  • Silane
  • Ammonia
  • Carbon Monoxide
  • Chlorine


Pyrophoric gases are classified as physical hazards under WHMIS 2015 and are category 1 – the most severe hazard category.

Warnings and Symbols

Pyrophoric gases are identified on labels using the “flame” pictogram.

Pyrophoric gases are further identified using the signal word “danger” and the hazard statement “Catches fire spontaneously if exposed to air.”

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