WHMIS: labels and safety data sheets

On a single day on Kingsway Tower, Maya might handle PVC primer and solvent cement, pipe thread sealant, flux and solder, cutting oil for the threading machine, spray foam sealant, propane for the torch and a cleaner for the fixtures. Each of these is a hazardous product. Some are flammable, some irritate the skin and eyes, some give off vapours that cause dizziness or long-term harm, and a few can do several of these things at once. The Workplace Hazardous Materials Information System, WHMIS, is Canada's system for telling workers about these hazards and how to work safely with them.

WHMIS has three parts that work together: labels on containers, safety data sheets (SDSs) with the full details, and worker education and training. Suppliers, meaning manufacturers, importers and distributors, must classify their products and provide the labels and SDSs under the federal Hazardous Products Act and Hazardous Products Regulations. Employers must make sure products in the workplace are labelled, make the SDSs available, and train workers, under provincial law; in Ontario that is the WHMIS regulation under the Occupational Health and Safety Act.

A system based on the GHS

Since 2015, WHMIS has been aligned with the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), a United Nations system used in many countries, including the United States. That is why a container of solvent cement bought in Canada and one bought in the United States now carry similar labels with the same red-bordered pictograms. Health Canada amended the Hazardous Products Regulations in December 2022 to align with a newer edition of the GHS (revision 7, with some parts of revision 8), and suppliers had a three-year transition that ended on December 14, 2025. Labels and SDSs Maya sees today should meet the updated rules.

For a worker, the details of the transition matter less than the result: the information on a label and an SDS is organized the same way no matter which supplier made the product, so once you can read one, you can read them all.

Hazard classes and pictograms

Hazardous products are classified into hazard classes, grouped as physical hazards (such as flammable liquids, gases under pressure and corrosives to metals) and health hazards (such as acute toxicity, skin corrosion and irritation, eye damage, respiratory sensitization, carcinogenicity and specific target organ toxicity). Each class is divided into categories by severity, with category 1 the most severe. The classification decides which pictograms, signal word and hazard statements appear on the label.

WHMIS has one pictogram that the GHS does not: biohazardous infectious materials, shown as a biohazard symbol inside a circle rather than a diamond. Plumbers working on existing drain and sewer lines meet this hazard regularly, because sewage carries bacteria and viruses that can cause serious illness. Lesson 11 covers the protective equipment and hygiene that go with it.

Reading a supplier label

The label from the supplier is the first thing Maya sees on a product. It must be in English and French, and must have a distinctive hatched border. It carries seven kinds of information.

Two words on the label carry a lot of weight. The signal word tells you how serious the worst hazard is: DANGER for the more severe categories, WARNING for the less severe, and no signal word for the least severe. The hazard statements tell you exactly what the hazard is. When Luis handed Maya her first can of solvent cement, he asked her to read the label aloud before opening it. She found the flame pictogram, the signal word DANGER and the statement about drowsiness, and he explained why they glue pipe only with a window open or a fan running, and never near the soldering torch.

Workplace labels and decanted products

Products often end up in containers other than the one they came in. Maya might pour cutting oil from a large drum into a small squeeze bottle, or mix a cleaning solution in a spray bottle. Once a product is transferred to another container, that container needs a workplace label. A workplace label is simpler than a supplier label: it must show the product identifier, information for safe handling (which can include pictograms), and a statement that an SDS is available. Workplace labels are also required on supplier containers whose label has been lost or become unreadable.

Unlabelled containers are one of the most common hazard communication problems on construction sites, and one of the most dangerous. A clear liquid in an unmarked bottle could be water, a cleaner, a solvent or an acid. Kingsway Tower's rule is simple: if a container has no label, nobody uses it, and it goes to the foreman to be identified or disposed of. Food and drink containers are never used for chemicals, because someone will eventually drink from one.

Safety data sheets

The safety data sheet is the detailed document behind the label. Every SDS has the same 16 sections in the same order, so with practice Maya will find what she needs in seconds. Some sections matter more to a worker than others.

The employer must make the SDS for every hazardous product in the workplace readily available to workers, on paper or electronically, as long as workers know how to get to it and it is accessible during every shift. On Kingsway Tower, Stonebridge keeps a binder in the site trailer, Northbridge keeps a binder in its gang box on each active floor, and both companies have the SDSs on a phone app. The SDS must be current: suppliers must update an SDS within 90 days of learning significant new information about the product.

Training: the part that makes it work

Labels and SDSs are useless if workers cannot read them. WHMIS training has two parts. General education covers how WHMIS works: the hazard classes, the pictograms, labels and SDSs. Workplace-specific training covers the products a worker actually uses: their hazards, the procedures for using, storing, handling and disposing of them safely, and what to do in an emergency. Ontario requires the employer to review the training at least once a year, or more often if conditions change or new information becomes available. Maya completed general WHMIS training in her pre-apprenticeship program; Northbridge gave her the workplace-specific training on her first day, and Luis covers each new product as she meets it.

Training also covers what to do when something goes wrong. If Maya splashes a product in her eyes, Section 4 of the SDS and the precautionary statements on the label both tell her what to do, usually rinsing with clean water for at least 15 minutes. The eyewash station on her floor is part of the system too. Lesson 12 covers first aid in more detail.

A day with hazardous products

Maya's work on the sixth floor shows how the pieces fit. In the morning she and Luis install PVC drain lines in four suites. Before starting, Maya checks the solvent cement label, opens the windows and runs a small fan to move the vapour away from where she is working, puts on safety glasses and the nitrile gloves the SDS recommends, and keeps the can closed between joints. When they finish, she wipes the drips, closes the cans and stores them in the flammables cabinet in the gang box, away from the propane cylinder.

In the afternoon they solder copper water lines. The flux label carries an exclamation mark and the statement that it causes skin irritation, so she keeps her gloves on and washes her hands before eating. The propane cylinder carries the flame and gas cylinder pictograms, and the hot work permit from Stonebridge requires a fire extinguisher at hand and a fire watch after the work. When the cleaner from the fixture supplier arrives in an unlabelled spray bottle, she does not use it. Dave finds the original container, fills out a workplace label and finds the SDS on the app. Ten minutes of care, three products, no exposures.