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Discovering the Event


More often than not, first responders arriving on scene will know beforehand if an event involves the accidental or intentional release of chemicals. However, there may be situations in which you will have to make a determination given only what the scene itself can tell you.

When you arrive, consider what the conditions, symptoms, and signs suggest:

  • Is there anything unusual in what you see?

  • Are there obvious signs that a chemical release is occurring or has occurred?

  • Are there less obvious signs?

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Obvious Signs of a Chemical Release

Chemical releases may be easily linked to events such as:

  • Industrial accidents, fires, or explosions

  • Transportation accidents

  • Agricultural accidents

Consider the following factors:

  • The location of the event - Did the event occur in or close to a facility that stores or uses chemicals? These facilities include but are not limited to:

    • Service stations

    • Hospitals

    • Hazardous materials waste sites

    • Chemical manufacturing plants

    • Research facilities

  • The nature of the event - Did the event occur while chemicals were being used or transported? Chemicals are most often released as a result of transportation accidents or because of chemical accidents in plants.

Look for signs that can immediately help you identify if chemicals were involved. At the site of a transportation accident, for example, placards, container labels, or shipping documents may indicate the presence of hazardous materials and even tell you what chemicals are involved. If an event occurs in or around a building, look for signs posted on doors or windows that warn of rooms or facilities where hazardous materials are used or stored.

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Less Obvious Signs of a Chemical Release

In the absence of more obvious indicators, chemical releases can often be characterized first by the rapid onset of symptoms in humans and wildlife in a localized area. Consider the:

  • Impacts on wildlife

    • Mass kills or sickness of animals, birds, fish, or insects

    • The absence of insects

  • Impacts on humans

    • Physical symptoms, including:

      • Difficulty breathing

      • Eye irritation

      • Loss of coordination

      • Nausea

      • Burning sensation in the nose, throat, and/or lungs

    • Mass casualties

    • Patterns to casualties

  • Impacts on the environment

    • Visual differences and anomalies

    • Dead, discolored, or withered vegetation

    • Oily sheens, coatings, or droplets on surfaces

    • Unusual puddles or powders

    • Unusual or uncharacteristic odors

    • Low-lying clouds

    • Bomb or munitions-like debris

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What to Look For

Look for large population effects, such as:

  • Large quantities of dead wildlife

  • Mass casualties or numerous victims exhibiting symptoms of chemical exposure

  • Large areas of dead, discolored, or withered vegetation

Look for geographic patterns, such as:

  • Dead fish, aquatic birds, and/or insects in and around nearby water sources

  • Differences in symptoms exhibited by people indoors versus people outdoors

  • Large patches, as opposed to small, dispersed areas of dead vegetation

  • Patterns of debris that could be caused by an explosion

  • Debris, packaging, or other items that appear misplaced

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Consider Other Explanations

The less obvious signs of a chemical release are uncommon. However, there may be other, less sinister explanations for them. For example:

  • Droughts could explain dead vegetation and lack of wildlife in the area

  • Meteorological conditions could explain the presence of low-lying clouds or puddles

  • Odors could come from nearby manufacturing plants, restaurants, etc.

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  1. Chemical/Biological/Radiological Incident Handbook (CIA)

  2. Chemical Threats (FEMA)

  3. 2012 Emergency Response Guidebook (PDF - 4.16 MB) (DOT PHMSA)

  4. Hazardous Materials Incidents (FEMA)

  5. How to Recognize if Chemical Agents Have Been Used (PDF - 14 KB) (North Dakota Department of Health)

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