Saturday, April 12, 2014

Understanding Chemical Hazards

An active rail line runs less than a block from our home. Six blocks the other way runs a major interstate highway. While it's unlikely we'll ever be directly affected by a hazardous chemical spill from a rail car or road trailer, I have to admit our chances are higher than for most. Hazardous chemicals can explode, burn, and poison. As I'm trying to factor this into my plans, here's what I'm coming up with.

If you come across what may be a chemical hazard, the important thing is not to rush in to help people who may have fallen. Stay upwind of the hazard, and make efforts to keep away from spilled liquids, vapors, fumes, smoke, and even suspicious containers. First responders will typically set up some kind of perimeter at this time to keep others out of danger.

Consider how the material might spread--now might be a great time to throw some sandbags in the gutter, for example, to keep a mysterious liquid from flowing down the street or down a storm drain. Just because you cannot see or smell anything does not mean invisible and odorless vapors or fumes are present, so note the wind conditions and any ventilation systems which may be in play. Some chemicals (including solids!) react with water to produce heat, explosions, or dangerous fumes.

If you can, identify the material. Look for a diamond-shaped placard or orange identification panel. Placards often have a symbol and/or a hazard class or division number in the lower quadrant which roughly corresponds to the most significant risk associated with the hazardous material. Orange identification panels often have a hazard identification number in the top half of the panel and a 4-digit identification code in the bottom half. Here's a guide to decode the division number from a placard or the hazard identification number from an orange panel:
  1. Explosives (placard may be orange)
  2. Gases (placard may be green, red if flammable, or yellow if corrosive)
  3. Flammable liquids (vapors) or self-heating liquids (placard may be red)
  4. Flammable solids or self-heating solids (placard may be blue)
  5. Oxidizing (fire-intensifying) effect (placard may be yellow)
  6. Toxic (poisonous) or infectious
  7. Radioactive
  8. Corrosive
  9. Miscellaneous dangerous substance
  • Doubling of a digit (i.e. 33) indicates an intensification of that hazard
  • When just a single digit is sufficient, on an orange placard that digit is followed by a zero (i.e. 50)
  • A hazard identification number beginning with the letter "X" means the material will react dangerously with water (i.e. X88)
  • When 9 appears as the 2nd or 3rd digit there may be a risk of spontaneous violent reaction
The 4-digit identification code and/or name of hazardous material will be useful when reporting an incident or seeking help.

The Pipeline and Hazardous Materials Safety Administration (PHMSA) publishes an Emergency Response Guidebook that expands on the material presented here, and provides safety recommendations for all forms of hazardous materials, which may be looked up by name or identification code. The safety recommendations include recommended perimeters for small and large spills, recommended protective gear, special instructions in case of fire, special instructions in case of leakage, and first aid for those suffering from exposure. Keep one of the Guidebooks in your vehicle, and consider whether you may need one at home, at work, etc. A PDF version of the PHMSA Emergency Response Guidebook is available free online.

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