Why hazard communication matters

Almost every workplace uses hazardous chemicals. Cleaning chemicals in a school, solvents in a print shop, fuels at a gas station, compressed gases in a hospital, battery acid in a warehouse, refrigerants in a data center and paints on a construction site can all cause fires, burns, poisoning, breathing problems or long-term illness if they are handled without the right information. OSHA's Hazard Communication Standard, often called HazCom or the "right-to-know" standard, is the federal rule that makes sure the people who use hazardous chemicals know what the hazards are and how to protect themselves. This course explains how HazCom works: how chemicals are classified, what labels and safety data sheets tell you, how to handle, store and respond to hazardous chemicals safely, and what employers, manufacturers, importers, distributors and workers must each do.

About this course

This is an awareness-level course. It gives you a solid general understanding of HazCom and of working safely with hazardous chemicals, and it can support the training that employers must provide. It does not replace the workplace-specific training your employer must give you on the actual chemicals, procedures and emergency arrangements at your workplace, and it does not replace other required training, such as DOT hazardous materials training, respiratory protection, HAZWOPER or first aid. Some states run their own OSHA-approved state plans with requirements that may differ, so always follow the rules and procedures that apply where you work, and ask your supervisor or safety committee if you are unsure.

How hazardous products harm people

Hazardous products can cause harm in two broad ways. Physical hazards come from the properties of the product itself: it may catch fire, explode, react violently with other materials, release gas under pressure, or corrode metal. Health hazards come from the product's effects on the body: it may poison you if swallowed, inhaled or absorbed through the skin; burn your skin or eyes; trigger allergies or asthma; damage organs such as the liver, lungs or nervous system; or cause cancer, genetic damage or harm to an unborn child after long or repeated exposure. Some effects are immediate and obvious, such as a chemical burn. Others are delayed or hidden, appearing months or years later, such as occupational asthma or cancer. Because many hazardous products look, smell and feel like ordinary liquids, powders or gases, you cannot rely on your senses to tell whether something is dangerous. That is why written hazard information on labels and safety data sheets is essential.

The right to know

Hazard communication rests on a simple principle: people have a right to know about the hazards they work with. This right developed through the twentieth century as occupational diseases became better understood. Workers in the past often handled chemicals labeled only with trade names, with no information about what was inside or how dangerous it was. Many suffered poisoning, cancer and other diseases that could have been prevented. Labor unions, health researchers and safety advocates campaigned for laws requiring that chemical hazards be disclosed and that workers be trained.

In the United States, OSHA issued the Hazard Communication Standard in 1983, initially for manufacturing, and expanded it to cover nearly all workplaces by 1987. The standard gave workers the right to know the identities and hazards of the chemicals they work with. Alongside other OSHA rights, such as the right to a safe workplace, to receive training in a language they understand, to file a complaint and to be protected from retaliation, the right to know is central to worker protection. In 2012, OSHA revised the standard to align with the international Globally Harmonized System (HCS 2012), and in 2024 it updated the standard again to follow later GHS revisions.

The Globally Harmonized System

Before the 2010s, countries classified and labeled chemicals in different ways. A product could be labeled "toxic" in one country and "harmful" in another, with different symbols, criteria and safety data sheet formats. This confused workers, made trade difficult and meant that hazards were communicated inconsistently. The United Nations developed the Globally Harmonized System of Classification and Labeling of Chemicals, known as the GHS, first published in 2003 and revised every two years since. The GHS provides common criteria for classifying chemical hazards, standard label elements such as pictograms, signal words and hazard statements, and a standard 16-section format for safety data sheets. The GHS is not a law itself; each country chooses which parts to adopt, through its own legislation. Canada and the United States have both adopted the GHS for workplace chemicals, which is why WHMIS and HazCom now look very similar, though there are some differences that this course points out. Lesson 2 explains the GHS and the legal framework in more detail.

The three main elements

HazCom rests on several connected elements, often summarized as:

• Labels on containers of hazardous chemicals, which alert you to the main hazards and the basic precautions.
• Safety data sheets (SDSs), which give detailed information about the product's hazards, safe handling, storage, emergency measures, properties and regulatory status.
• Information and training, which helps you understand the labels and SDSs and know the specific procedures for working safely with the chemicals at your workplace, together with a written hazard communication program and a chemical inventory maintained by the employer.

These elements work together. A label gives a quick warning at the point of use; the SDS gives the full picture; training makes sure people can understand and act on the information. If any element is missing, hazard communication fails: a perfectly labeled drum is little use if workers do not know what the pictograms mean, and a complete SDS filed away where no one can find it protects no one.

Who is involved

HazCom gives different groups different duties. Chemical manufacturers and importers must evaluate (classify) the chemicals they produce or import and prepare labels and SDSs; distributors must pass these on to customers. Employers must have a written hazard communication program, keep a list of hazardous chemicals in the workplace, make sure containers are labeled, keep SDSs readily accessible and train employees. Employees should take part in training, follow safe work practices, use the controls and protective equipment provided, and report hazards such as damaged or missing labels. Lesson 12 discusses these duties in detail.

What hazard communication covers and does not cover

HazCom applies to hazardous chemicals, meaning any chemical that is classified as a physical or health hazard, a simple asphyxiant, combustible dust or a hazard not otherwise classified. Some items are covered by other laws or are exempt from labeling requirements, including pesticides labeled under FIFRA, food, drugs and cosmetics regulated by the FDA, distilled spirits and tobacco, consumer products used in the workplace in the same way and amounts as a typical consumer would, hazardous waste regulated under RCRA, wood and wood products (unless chemically treated or likely to be cut or sanded in ways that create combustible dust), and articles. Even when an item is exempt from HazCom labeling, employers still have a general duty under the Occupational Safety and Health Act to protect workers from recognized hazards.

Hazard communication and other safety rules

HazCom is one of several systems for communicating chemical hazards. The Department of Transportation's hazardous materials regulations govern labels, placards and shipping papers when chemicals are transported; DOT labels and placards look different from HazCom labels and serve emergency responders during transport. Consumer products sold in stores carry labels under Consumer Product Safety Commission rules, and pesticides carry labels approved by the Environmental Protection Agency. Workplace exposure limits, ventilation, respiratory protection, laboratory standards and confined space rules are set by other OSHA standards. Fire codes, often based on NFPA standards, set rules for storing flammable liquids and other hazardous materials. A chemical may carry several types of labels during its life: a DOT label on the shipping package, a HazCom label on the container, and a workplace label on a smaller container filled at work.

Why it matters: the cost of failure

Failures of hazard communication cause serious injuries and deaths every year. Common scenarios include workers mixing bleach with an ammonia-based or acidic cleaner, producing toxic gases; using a flammable solvent near an ignition source because the container had no label; entering a tank or pit without knowing that a previous product could release toxic vapor; transferring a chemical into an unlabeled drink bottle that someone later drinks from; and developing occupational asthma after months of exposure to a sensitizer that no one recognized as hazardous. Each of these could have been prevented by a clear label, an accessible SDS and training. Hazard communication violations are consistently among the most frequently cited workplace safety violations, showing how often the basics are missed.

How this course is organized

Lesson 2 explains the GHS and the legal framework. Lessons 3 and 4 explain how physical and health hazards are classified. Lesson 5 covers pictograms, signal words and hazard and precautionary statements. Lessons 6 and 7 cover supplier and workplace labels. Lessons 8 and 9 cover safety data sheets and how to read them. Lesson 10 covers exposure, exposure limits and controls, Lesson 11 safe handling, storage, spills and emergencies, and Lesson 12 roles, training, programs and the capstone.

Key words to know from the start

A few terms recur throughout the course. A hazard is anything with the potential to cause harm; risk is the likelihood and severity of harm in a particular situation, which depends on exposure. Exposure means contact with a hazardous product, whether by breathing it, touching it, swallowing it or having it injected. Controls are measures that reduce exposure or the chance of an incident, from eliminating a product to wearing gloves. Keeping these ideas separate helps you understand why a highly hazardous product can sometimes be used safely, and why a seemingly mild one can cause harm when exposure is high.

Throughout the course, look for the products you actually use at work and compare their labels and SDSs with the examples. Applying each lesson to real products is the best way to turn awareness into safe habits.