Emergency Response Guidebook

How to use the table of initial isolation and protective action distances

[EDITOR'S NOTE: This document was copied verbatim from the 2004 Emergency Response Guidebook. There may be references to parts of the 2004 ERG or to formatting styles (e.g. colors) that we did not implement in this online version that would be found within an actual printed copy of this book.]

  1. The responder should already have:
    • Identified the material by its ID Number and Name; (if an ID Number cannot be found, use the name of material index)
    • Found the three-digit guide for that material in order to consult the emergency actions recommended jointly with this table;
    • Noted the wind directions.
  2. Look in this Table for the ID Number and Name of the Material involved in the incident. Some ID Numbers have more than one shipping name listed - look for the specific name of the material. (If the shipping name is not known and the Table lists more than one name for the same ID Number, use the entry with the largest protective action distances.)
  3. Determine if the incident involves a SMALL or LARGE spill and if DAY or NIGHT. Generally, a SMALL SPILL is one which involves a single, small package (e.g., a drum containing up to approximately 200 liters), a small cylinder, or a small leak from a large package. A LARGE SPILL is one which involves a spill from a large package, or multiple spills from many small packages. DAY is any time after sunrise and before sunset. NIGHT is any time between sunset and sunrise.
  4. Look up the initial ISOLATION distance. Direct all persons to move, in a crosswind direction, away from the spill to the distance specified - in meters and feet.
  5. Look up the initial PROTECTIVE ACTION DISTANCE shown in the Table. For a given dangerous goods, spill size, and whether day or night, the Table gives the downwind distance - in kilometers and miles - for which protective actions should be considered. For practical purposes, the Protective Action Zone (i.e., the area in which people are at risk of harmful exposure) is a square, whose length and width are the same as the downwind distance shown in the Table.
  6. Initial Protective Actions to the extent possible, beginning with those closest to the spill site and working away from the site in the downwind direction. When a water-reactive TIH producing material is spilled into a river or stream, the source of the toxic gas may move with the current or stretch from the spill point downstream for a substantial distance.

The shape of the area in which protective actions should be taken (the Protective Action Zone) is shown in this figure. The spill is located in the center of the small circle. The large circle represents the INITIAL ISOLATION zone around the spill.

NOTE: See "Introduction To The Table Of Initial Isolation And Protective Action Distances" for factors which may increase or decrease Protective Action Distances.

Call the emergency response telephone number listed on the shipping paper, or the appropriate response agency as soon as possible for additional information on the material, safety precautions, and mitigation procedures.


WARNING: These pages are for general reference and educational purposes only and MUST NOT be relied upon as a sole source to determine regulatory compliance or where matters of life and health are concerned. This site and the author do not warrant or guarantee the accuracy or the sufficiency of the information provided and do not assume any responsibility for its use.

To ensure regulatory compliance when transporting hazardous materials or dangerous goods, one must receive proper training and certification from a qualified instructor and refer to the current year's Code of Federal Regulations Title 49 (49CFR) or your country's shipping regulations. In matters regarding workplace safety, refer to current OSHA regulations (29CFR) and NIOSH guidelines or your own country's health and safety regulations. No one should ever enter into a hazardous environment without proper training from qualified instructors.

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