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663 HAZWOPER for General Site Workers IV
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Forms of Hazardous Chemicals

You might think that the chemicals which apply to the rule are those in liquid, gas or particulate form. But, the standard's definition of "chemical" is much broader than that commonly used. Per the Hazard Communication Standard, chemicals that apply may exist in one of many forms:

  • Dusts - are finely divided particles. Example - wood dust.
  • Fumes - are even smaller particles usually formed when solid metal is heated and vaporized, and then condenses as tiny particles.
  • Fibers - are like dusts but are of an elongated shape. Examples - asbestos and fiberglass.
  • Mists - are liquid droplets that have been sprayed into the atmosphere.
  • Vapors - are gases formed when liquid evaporates. A vapor is the gaseous phase of a substance which is a normally a liquid or solid at room temperature.
  • Gases - are substances that are normally airborne at room temperature.
  • Solids - such as metal, treated wood, plastic.
  • Liquids - the most common form in the workplace.

Knowledge Check Choose the best answer for the question.

2-4. Small particles that are usually formed when solid metal is heated and vaporized are called _____.