WHMIS Symbols & Pictograms: All 10 Hazard Symbols Explained

WHMIS uses 10 hazard pictograms — red-bordered diamonds that show, at a glance, why a chemical product is dangerous. They're set by the Hazardous Products Regulations, aligned with the global GHS standard, and you'll find them on supplier labels and safety data sheets across Canadian workplaces. Nine are assigned to WHMIS hazard classes; the tenth, the environment pictogram, is optional in Canada. 1

Quick-reference chart: all 10 WHMIS pictograms

Not every hazardous product carries a pictogram. Some hazard classes and categories require none — the label still carries a signal word, hazard statements and the other required elements its classification calls for. The absence of a red diamond does not mean the product is safe: read the label and the safety data sheet. 2

Flame (Flammable)

The flame pictogram means a product catches fire easily. It covers flammable gases, aerosols, liquids and solids, and also the products that can ignite without an external flame at all: pyrophoric substances that ignite on contact with air, self-heating substances, substances that emit flammable gases in contact with water, most self-reactive substances and organic peroxides, and chemicals under pressure. 1

Where you'll see it: solvents and thinners, aerosol adhesives and sprays, fuels and fuel additives, alcohol-based cleaning products, some paints and coatings.

What to do: keep the product away from heat, sparks, static discharge and open flame; do not smoke nearby; store in the conditions the safety data sheet specifies, and keep containers closed and grounded when the SDS calls for it. Check section 7 of the SDS before you decide where to store it.

Flame Over Circle (Oxidizing Materials)

The flame over circle pictogram means a product can cause or intensify a fire by releasing oxygen. Oxidizers do not have to burn themselves — they feed the fire in whatever is around them, which is why an oxidizer stored beside a flammable is a far bigger hazard than either alone. It covers oxidizing gases, liquids and solids.

Where you'll see it: pool and water-treatment chlorination products, hydrogen peroxide solutions, some bleaches, nitrates and certain industrial cleaning chemicals.

What to do: store oxidizers away from flammables, combustibles and organic material, and follow the separation distances in the SDS. Keep them off wooden shelving and away from rags, cardboard and sawdust. Clean up spills immediately — dried oxidizer on a combustible surface is an ignition source.

Gas Cylinder (Gases Under Pressure)

The gas cylinder pictogram means the contents are stored under pressure — as a compressed gas, a liquefied gas, a dissolved gas or a refrigerated liquefied gas. The hazard is the container as much as the contents: a cylinder that is heated can rupture violently even if the gas inside is harmless, and refrigerated liquefied gases can cause cryogenic burns on contact.

Where you'll see it: welding and cutting gases, propane, oxygen and medical gases, CO₂ cylinders for beverage systems, refrigerants, and compressed air.

What to do: secure cylinders upright with a chain or strap, keep valve caps on when they are not in use, keep them away from heat sources and direct sun, and never drop, drag or roll a cylinder. Move them on a proper cart, and treat a damaged cylinder as an emergency, not a maintenance job.

Corrosion (Corrosive Materials)

The corrosion pictogram means a product causes severe skin burns and eye damage, or is corrosive to metals, or both. "Severe" is the operative word: this is the classification for products that destroy tissue on contact rather than irritating it. Products that only irritate carry the exclamation mark instead.

Where you'll see it: drain and oven cleaners, battery acid, strong caustic and acidic cleaning products, descalers, and some concrete and masonry products.

What to do: wear the gloves and eye or face protection the SDS specifies — for corrosives the SDS will usually name a material, not just "gloves". Know where the nearest eyewash station and safety shower are before you open the container, and know how long you are expected to flush for. Never mix corrosives with other cleaning products.

Exploding Bomb (Explosion and Reactivity Hazards)

The exploding bomb pictogram means a product may explode from heat, shock, friction or contamination. Under WHMIS it marks the most unstable self-reactive substances and organic peroxides. It does not mean "explosives": explosives as defined in the Explosives Act are excluded from WHMIS altogether and are regulated separately — a detail many sources get wrong. 4 Being honest about frequency also matters: outside specific industries and laboratories, most Canadian workers will never handle a product bearing this pictogram.

Where you'll see it: certain laboratory reagents, and some organic peroxides used in plastics, resins and composites.

What to do: follow the SDS storage instructions exactly — temperature limits on these products are not advisory. Control heat, shock and friction, keep quantities to a minimum, and never improvise handling. If your workplace stores products in this class, the site-specific procedures are part of your WHMIS training, not optional reading.

Skull and Crossbones (Acute Toxicity)

The skull and crossbones pictogram means acute toxicity — the product can cause death or serious harm by swallowing, skin contact or inhalation, in the most severe categories (1, 2 and 3). Acute toxicity is the only endpoint it covers. Products whose danger lies in a different endpoint — cancer, organ damage, sensitization — carry the health hazard pictogram instead, even where that harm can follow a single exposure.

Where you'll see it: certain pesticides and fumigants, some industrial cleaning and stripping products, methanol, and a range of laboratory chemicals.

What to do: use exactly the personal protective equipment the SDS specifies, work with the ventilation the SDS specifies, and never work with these products without WHMIS training and site-specific procedures. Know the first-aid measures in section 4 before you start, not after something happens.

Health Hazard (Serious Long-Term Health Effects)

The health hazard pictogram means a serious health hazard — carcinogenicity, germ cell mutagenicity, reproductive toxicity, respiratory sensitization, specific target organ toxicity, or aspiration hazard.

This is the pictogram people most often confuse with the skull and crossbones, and the difference is the endpoint, not the timing: skull and crossbones means acute toxicity; the health hazard pictogram means one of the serious health endpoints listed above. Some of those effects are delayed by years, but not all of them are — and a product with this symbol may feel entirely harmless while you are using it. 1

Where you'll see it: crystalline silica-containing products, some solvents and degreasers, certain paints, isocyanate-containing products, and some fuels.

What to do: engineering controls first — ventilation, enclosure, dust suppression — then the PPE and respiratory protection the SDS specifies. Follow exposure limits, and take the housekeeping rules seriously; long-term hazards are managed by reducing dose, not by feeling fine at the end of the shift.

Exclamation Mark (Irritation and Less Severe Hazards)

The exclamation mark pictogram is the "less severe" warning — skin and eye irritation, skin sensitization, the milder acute toxicity category, and short-term effects like narcotic effects or respiratory irritation. It is also an easy pictogram to shrug off — "less severe" does not mean harmless, and skin sensitization in particular is permanent once it develops. 1

Where you'll see it: many everyday workplace cleaners and detergents, adhesives, some paints, and a large share of maintenance products.

What to do: avoid skin and eye contact, wear the gloves the SDS specifies, wash after handling and before eating, and stop using a product and report it if you develop a rash or reaction — sensitization gets worse with each exposure, not better.

Environment (Aquatic Toxicity)

The environment pictogram means the product is harmful to aquatic life — and here is the Canada-specific fact many sources get wrong: this pictogram is not assigned to any WHMIS hazard class.

Canada did not adopt the GHS environmental hazard classes into the Hazardous Products Regulations, so no Canadian supplier is required to display it — but many do, because the same product is sold internationally under GHS. That is why it belongs on a list of ten symbols you will encounter, and why only nine of them are WHMIS classifications. 13

Where you'll see it: some pesticides, oils and lubricants, marine coatings, and imported products labelled to an international standard.

What to do: prevent release to drains, storm sewers, soil and waterways; use containment when decanting; and dispose of the product and its packaging according to section 13 of the SDS and your local environmental rules.

Biohazardous Infectious Materials (Canada-Specific)

The biohazardous infectious materials pictogram means micro-organisms, viruses or their toxins that can cause disease in people or animals. This is Canada's own symbol: it is not part of GHS, and it was carried across from WHMIS 1988 because Canada regulates infectious materials in the workplace under WHMIS where most GHS jurisdictions do not. If you see it, you are looking at a Canadian classification. 1

Where you'll see it: clinical, research and veterinary laboratories, healthcare and diagnostic settings, and some waste-handling operations.

What to do: containment procedures, biosafety requirements and specific training come before handling — this class is not covered by generic WHMIS education alone. Follow your facility's biosafety manual, and treat exposure as a reportable incident.

Old WHMIS 1988 symbols vs today's pictograms

Workers trained before 2015 learned a different set of symbols: black-and-white images inside a circle, grouped into classes A to F. Those symbols are gone from new labels, but the products did not change. Here is how the old classes map onto the pictograms in use today under the GHS standard.

WHMIS 1988 (circle)	Since 2015 (red diamond)	What changed
Class A — Compressed gas	Gas cylinder	Same meaning; the symbol changed
Class B — Flammable and combustible material	Flame	Same core meaning, GHS-standard symbol; self-heating and pyrophoric substances now explicit
Class C — Oxidizing material	Flame over circle	Same meaning, GHS-standard symbol
Class D1 — Poisonous, immediate and serious effects	Skull and crossbones, or exclamation mark	Now split by acute toxicity category: the most severe categories take the skull, the milder category takes the exclamation mark
Class D2 — Poisonous, other toxic effects	Health hazard, or exclamation mark	Now split by endpoint: carcinogenicity, mutagenicity, reproductive toxicity, sensitization and organ toxicity take the health hazard symbol; irritation and skin sensitization take the exclamation mark
Class D3 — Biohazardous infectious material	Biohazardous infectious materials	Unchanged in meaning and retained as a Canada-specific pictogram
Class E — Corrosive material	Corrosion	Same meaning; corrosive-to-metals is now stated explicitly
Class F — Dangerously reactive material	Exploding bomb, and/or hazard statements on the label	The single 1988 class was redistributed across self-reactives, organic peroxides and the reactivity information in sections 7 and 10 of the SDS
(no equivalent)	Environment	New under GHS; not mandatory in Canada
Hatched border on supplier labels	No border required	The 1988 hatched border is no longer required, though it is not prohibited

Where you'll see pictograms: labels and SDSs

Pictograms do not appear on their own — they reach you through two documents. The first is the supplier label, which carries the pictograms the product's classification requires; a workplace label, created on site, may reproduce them but is not required to — see supplier and workplace labels for how the two types differ.

The second is the safety data sheet, where the pictograms or symbol names appear in section 2 of the safety data sheet alongside the signal word and hazard statements, so you can confirm the symbol on the drum matches the document that explains it.

Labels, safety data sheets and the classification behind them are the key components of WHMIS, and pictogram recognition is only useful when you can read all three together.

Do you need to know these for WHMIS certification?

Yes — pictogram recognition is part of WHMIS education everywhere, and it is evaluated in our course. It is also an area where many people lose marks, usually by confusing the skull and crossbones with the health hazard symbol, or by not knowing that the biohazard symbol is Canada-specific. The eSafetyFirst course takes about 1 hour 45 minutes online and issues the certificate immediately; the site-specific half — your own workplace's products and procedures — stays with your employer.