WHMIS PICTOGRAMS QUICK REFERENCE — ALL 9 SYMBOLS EXPLAINED

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Every hazardous product on a Canadian construction site carries a label with one or more diamond-shaped pictograms — red-bordered symbols on a white background that communicate the type of hazard at a glance. These pictograms are part of the Globally Harmonized System (GHS), adopted into Canada's Workplace Hazardous Materials Information System (WHMIS 2015, now simply called WHMIS).

Understanding these nine symbols is not optional. WHMIS training is a legal requirement for every worker who handles, stores, or works near hazardous products. This quick reference breaks down each pictogram, explains the hazard it represents, and gives real construction chemical examples you will encounter on the job.

1. Flame — Flammable Materials

The flame pictogram indicates products that can catch fire easily. This includes flammable liquids, gases, aerosols, and solids, as well as self-reactive substances and pyrophoric materials (substances that ignite spontaneously in air).

• Construction examples — gasoline, acetone, contact cement, spray paint, propane, lacquer thinner, MEK (methyl ethyl ketone), and many adhesives and sealants
• Key precaution — keep away from heat, sparks, open flames, and hot surfaces. Store in approved flammable storage cabinets. Use in well-ventilated areas.

2. Exploding Bomb — Explosive Materials

This pictogram identifies products that can explode or are self-reactive under certain conditions — heat, shock, or friction. The explosion may produce gas, heat, and shrapnel.

• Construction examples — powder-actuated tool cartridges (Hilti shots), certain organic peroxides used in resin curing, and blasting agents used in excavation and demolition
• Key precaution — handle gently. Avoid heat, shock, friction, and static discharge. Store in designated explosive storage areas as required by regulations.

3. Flame Over Circle — Oxidizers

The oxidizer pictogram shows a flame above a circle and indicates substances that can cause or intensify a fire by supplying oxygen. Oxidizers make other materials burn faster and hotter — even materials that would not normally ignite easily.

• Construction examples — calcium hypochlorite (used for water treatment in civil projects), potassium permanganate, certain bleaching agents, and some concrete admixtures containing oxidizing compounds
• Key precaution — keep away from flammable and combustible materials. Never store oxidizers next to fuels, solvents, or organic materials.

4. Gas Cylinder — Compressed Gas

This pictogram indicates gases stored under pressure in cylinders or containers. The hazard is the pressure itself — a damaged or overheated cylinder can become a projectile, and rapid release of gas can cause asphyxiation in enclosed spaces.

• Construction examples — oxygen cylinders, acetylene tanks (for welding and cutting), argon and CO2 (for MIG/TIG welding), nitrogen, and propane tanks
• Key precaution — store upright and secured with chains or straps. Keep away from heat sources. Never tamper with valves or regulators. Separate oxygen from fuel gases by at least 6 metres or by a fire-rated barrier.

5. Corrosion — Corrosive Materials

The corrosion pictogram shows a substance eating through a surface and a hand. It indicates products that can cause severe burns to skin, serious eye damage, or corrosion to metals on contact.

• Construction examples — muriatic acid (hydrochloric acid, used for masonry cleaning), sulfuric acid (in batteries), drain cleaners, certain concrete etching products, and some industrial degreasers
• Key precaution — wear chemical-resistant gloves, splash goggles, and face shield. Have an emergency eyewash station accessible within 10 seconds of travel. Never mix corrosive products with other chemicals.

6. Skull and Crossbones — Acute Toxicity (Severe)

This pictogram indicates products that can cause death or serious illness through a single exposure or short-term exposure — via ingestion, skin contact, or inhalation. These are the most immediately dangerous chemical hazards.

• Construction examples — methanol (sometimes used as antifreeze in concrete), certain pesticides used on construction sites adjacent to agricultural land, hydrogen cyanide (released when some materials burn), and some industrial-grade solvents
• Key precaution — avoid all contact. Use in a fume hood or with respiratory protection. Know the location of the Safety Data Sheet and emergency procedures before handling.

7. Health Hazard — Chronic/Serious Health Effects

The health hazard pictogram (a silhouette of a person with a starburst on the chest) indicates products that can cause serious long-term health effects — carcinogenicity, reproductive toxicity, organ damage, respiratory sensitization, or mutagenicity. These effects may not appear immediately but develop over time with repeated exposure.

• Construction examples — crystalline silica dust (from cutting concrete, stone, and brick), asbestos-containing materials (in renovation and demolition), certain epoxy resins and hardeners, isocyanates (in spray foam insulation), and formaldehyde (in some adhesives and resins)
• Key precaution — this is the pictogram that should concern construction workers the most. Many of these substances cause cancer or irreversible lung damage with chronic exposure. Use engineering controls (wet cutting, ventilation), wear appropriate respiratory protection, and monitor exposure levels.

8. Exclamation Mark — Irritation and Other Hazards

The exclamation mark pictogram covers a range of less severe (but still significant) health hazards — skin and eye irritation, skin sensitization (allergic reactions), acute toxicity (harmful but not lethal at lower doses), narcotic effects, and respiratory tract irritation.

• Construction examples — Portland cement (causes skin irritation and sensitization), many general-purpose cleaners and degreasers, certain wood preservatives, spray adhesives, and caulking compounds
• Key precaution — wear appropriate PPE (gloves, safety glasses). Wash hands thoroughly after handling. Just because the hazard is less severe than the skull and crossbones does not mean you can ignore it — repeated skin contact with cement, for example, can cause chronic dermatitis and chemical burns.

9. Environment — Aquatic Toxicity

The environment pictogram (a dead fish and tree) indicates products that are toxic to aquatic organisms. While this pictogram is not mandatory under WHMIS in Canada, many suppliers include it voluntarily, especially on products imported from jurisdictions where it is required.

• Construction examples — diesel fuel, hydraulic oil, certain wood preservatives (copper-based), anti-freeze (ethylene glycol), and some concrete curing compounds
• Key precaution — prevent spills and runoff into storm drains, waterways, and soil. Have spill kits on-site. Follow your site's environmental management plan for proper storage and disposal.

Reading WHMIS Labels — The 6 Required Elements

Every WHMIS supplier label must include six standardized elements. Knowing where to look helps you get critical safety information in seconds:

• Product identifier — the product name, matching the name on the Safety Data Sheet (SDS)
• Pictogram(s) — one or more of the nine symbols described above
• Signal word — either "Danger" (more severe hazard) or "Warning" (less severe hazard)
• Hazard statement(s) — standardized phrases describing the nature of the hazard (e.g., "Highly flammable liquid and vapour")
• Precautionary statement(s) — recommended measures to minimize exposure and handle emergencies
• Supplier identifier — name, address, and phone number of the Canadian supplier or manufacturer

The SDS Connection

Pictograms and labels are the first line of information, but the Safety Data Sheet (SDS) is the complete reference. Every hazardous product must have a corresponding 16-section SDS available at the workplace. The SDS provides detailed information on composition, first aid, fire-fighting measures, exposure controls, toxicological data, and disposal procedures.

If you see a pictogram you do not recognize, or if you are unsure about safe handling procedures, stop and consult the SDS before proceeding. Every Ontario construction site is required to maintain accessible SDS files for all hazardous products in use. If you cannot find the SDS, report it to your supervisor — it is a legal requirement, not a convenience.