WHMIS: How Many Physical Health Hazard Classes Are There?
In WHMIS 2015, there are 20 physical health hazard classes-and WHMIS 2015 also uses a separate set of health hazard classes (for health effects) that are counted separately from physical hazards.
Hazard classes in WHMIS are the building blocks that define what dangerous properties a product has and how those properties must be communicated at Canadian workplaces.
Direct answer: the exact number
The number you're asking for-physical hazard classes in WHMIS 2015-is 20.
This 20-count refers to the physical hazards group, while WHMIS 2015 also separately lists health hazards under a different group, rather than lumping them into the same total.
What "physical health hazard" usually means
People often say "physical health hazard" when they actually mean "physical hazards" (like flammability or reactivity) versus "health hazards" (like carcinogenicity or toxicity).
In WHMIS 2015 training materials, the system is presented as two major hazard groups-physical and health-each subdivided into classes.
- Physical hazards group: properties related to how a substance behaves (e.g., reactivity, flammability, corrosion potential).
- Health hazards group: properties related to health effects the product can cause.
- Separate counting: the "20" you're looking for is the physical hazard classes total, not a combined physical+health total.
WHMIS 2015 structure at a glance
WHMIS 2015 organizes hazards into groups, then into hazard classes, and each class has at least one hazard category (or type).
That's why you'll see documents explicitly listing "Physical Hazard Classes" and "Health Hazard Classes" rather than mixing them together.
- Identify the product's hazard group (physical or health).
- Use the matching hazard class within that group (e.g., for physical hazards).
- Apply the hazard category/type to determine severity level communication requirements.
| WHMIS 2015 hazard group | Number of hazard classes | What it communicates |
|---|---|---|
| Physical hazards | 20 | Physical/chemical behavior risks (reactivity, flammability, etc.) |
| Health hazards | 12 | Health-effect risks (toxicity, etc.) |
The table above mirrors a common WHMIS 2015 breakdown where the physical group is shown as 20 classes and the health group as 12 classes.
Why the "20" matters in practice
When you build workplace WHMIS documentation (labels, SDS, and training), you need to map each chemical to the correct hazard class so workers receive accurate emergency and handling information.
If you mistakenly treat "physical" and "health" classes as one combined count, your training scope and SDS review process can become inconsistent with how the system is structured.
"WHMIS applies to two major groups of hazards: physical and health."
Historical context: why WHMIS is organized this way
WHMIS 2015 aligns Canadian workplace hazard communication with the Globally Harmonized System approach, which uses groups, classes, and categories/types to standardize communication across jurisdictions.
That standardization is one reason training materials emphasize that the two groups are counted separately, including the physical-hazard class total of 20.
Quick reference numbers
If you're building a compliance checklist, the key number for your question-physical hazard classes-is 20 under WHMIS 2015.
For completeness, WHMIS 2015 materials often describe health hazard classes as 12 (a separate group), so you can cross-check your totals during audits.
| Metric | Value for WHMIS 2015 | Used for |
|---|---|---|
| Physical hazard classes | 20 | Classifying physical/chemical behavior hazards |
| Health hazard classes | 12 | Classifying health-effect hazards |
| Physical vs. health separation | Separate groups | Ensuring correct labeling/SDS hazard mapping |
These figures and structural principles are reflected in widely used WHMIS 2015 training and guidance materials that explicitly state the counts for physical and health hazard classes.
Safety takeaway: If you need the single number for the phrase "physical health hazard classes in WHMIS," use 20-because it corresponds to the physical hazard classes group total in WHMIS 2015.
Key concerns and solutions for How Many Physical Health Hazard Classes In Whmis
How many physical hazard classes are in WHMIS?
There are 20 physical hazard classes in WHMIS 2015.
Is "physical health hazard" the same as WHMIS physical hazards?
No-WHMIS distinguishes "physical hazards" (physical/chemical behavior) from "health hazards" (health effects), and the counts are tracked separately.
Does WHMIS count physical and health hazard classes together?
Typically, no: WHMIS 2015 describes two hazard groups (physical and health) and provides separate class totals for each.
Where do hazard categories fit?
Each hazard class has at least one hazard category (or type), which helps determine the level of hazard communicated on labels/SDS.