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April 10, 2013
Trainer's handbook: What is a hazardous chemical, anyway?

When your workers hear the phrase “hazardous chemical,” what do they think of? Reagents in a laboratory? Acid mist in the water treatment area? Lubricating oils in the machine shop?

Do they realize that not all hazardous chemicals are liquids or vapors, or that some otherwise harmless chemicals like nitrogen can become very hazardous indeed under certain conditions? Make sure your workers grasp the full range of possibilities that the term “hazardous chemicals” encompasses.

Background on chemical safety

Who needs to be trained? OSHA’s Hazard Communication (HCS or HazCom) standard requires you to train employees to work safely with the hazardous chemicals in their work area when they are initially assigned to that area and whenever a new hazard is introduced.

Why train workers in chemical safety? Workers need to know how to handle hazardous chemicals without exposing themselves or others to those hazards.

Hazardous chemical basics

Instructions to Trainer: This training session is compliant with the Globally Harmonized System of Classification and Labeling of Chemicals (GHS); the definitions and descriptions below are consistent with the new GHS standard.

What is a hazardous chemical? Is it the degreaser in the dip tank or dust that accumulates on the rafters? Where are hazardous chemicals found? Are they only in the flammables cabinet, or do they run through those pipes along the ceiling?

It’s important to understand what makes a chemical hazardous, where you might encounter a hazardous chemical, and what constitutes exposure to a hazardous chemical. Knowing these things better equips you to protect yourself.

What is a hazardous chemical? A chemical is considered hazardous if it poses:

  • A physical hazard. Chemicals that are flammable, explosive, reactive, or corrosive to metals fall into this category—they have the potential to cause physical damage to people and property. This category also includes chemicals that are only hazardous because of the form in which they are found. For example, nitrogen is not ordinarily a physical hazard, but if it is packaged as a compressed gas, it poses an explosion hazard.
  • A health hazard. Chemicals are considered health hazards if they:
  • Practice Tip

    Remember that a chemical is not always something in a container, with a label; the greatest hazard may be a chemical that is neither.

    • Can cause adverse health effects immediately, after a long delay, or over an extended exposure period (that is, if they are acutely or chronically toxic);
    • Are irritating or corrosive to the skin;
    • Can cause skin or respiratory sensitization or allergies, mutations or cancer, or reproductive toxicity;
    • Are toxic to specific organs or organ systems; or
    • Are toxic by aspiration.

Where are hazardous chemicals found? Hazardous chemicals may be easy to identify, like the chemicals in a diked tank farm on an industrial site. They may also be less obvious, like the finely divided dusts that accumulate on top of structural members inside a building that are not labeled.

Don’t just think of hazardous liquids with prominent labels when you think of hazardous chemicals. Understand that they can also be found as:

  • Unlabeled liquids. In particular, be wary of the contents of unlabeled pipes, which may be toxic, corrosive, or dangerous because of their temperature (for example, the steam in steam piping).
  • Solids. Some solids are hazardous chemicals. The most well-known example is probably asbestos, which is found in many older buildings.
  • Gases, mists, vapors, and fumes. When heated, sprayed, melted, or simply left uncovered, many hazardous liquids will evaporate or form airborne mists, vapors, and fumes. Clearly, these won’t be labeled, although they have great potential for harm—both as health hazards (when they are inhaled or settle on the skin) and as physical hazards (if they are generated from flammable liquids).

How can you be ‘exposed’ to a hazardous chemical? You probably know that inhaling a toxic chemical or getting a corrosive or toxic liquid on your skin is a dangerous exposure, but these are not the only ways you can be exposed to a hazardous chemical.

You can also be exposed by:

  • Ingestion. Most workers won’t knowingly eat dangerous chemicals, but if you don’t wash before your break, you could unintentionally ingest them. Always wash your hands before you eat, drink, or smoke. Also, if food and drink are forbidden in your work area, is it because hazardous chemicals could settle on them at your workstation? This could be another source of accidental ingestion.
  • Injection. Most common in healthcare, research, and veterinary environments, injection occurs when a chemical is introduced under the skin. If you combine hazardous chemicals and sharp objects, beware of the possibility of injection.


Don’t let hazardous chemicals sneak up on you; understand that these chemicals come in many forms and can be found in unexpected places. Follow the measures that have been put in place in your work area to protect your safety and health.

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