You've seen the numbers on the placards on trucks. What do they mean? If one of these trucks gets into an accident are you safe? How far away do you need to get? Is that distance downwind or upwind? There is a small book out that is worth keeping in your vehicle. Leaving it home in your library won't do you much good. It's an Emergency Response Guidebook: A Guidebook for First Responders During the Initial Phase of a Dangerous Goods/Hazardous Materials Transportation Incident. This book provides an index of all the codes. It also gives you the safety recommendations and emergency response information to protect yourself and the public. There is a table of placards and codes to provide a quick response.
Sometimes vehicles will have placards with pictures or numbers. They may also be different colors. You may have a placard that says 2.1. That's flammable gases. Others may just be numbered. Let take 33/1203 or even 1203. Most people recognize 1203 by the type of truck it's in. This is listed as gasoline/ petrol/ motor spirit. 33 is a European and South American code, but trucks in the US sometimes carry it as well. 3 is flammability of liquids (vapors) or gases or self-heating liquid. The number 33 means double the problem. If it was just a 3 then a 0 would be put after it, 30.
Substance 1203 lists code 128 as the proper response. Listed are the potential hazards including explosion, vapors, runoff, etc. It also lists potential health hazards. Next is public safety. How far away should people be evacuated. Even if you aren't on scene to help, at least you will quickly know how far away to get yourself and your family!
Next comes the emergency response. If there is a fire the book tells you what to use to put it out. Remember some substances will get worse if you put water on them. Fortunately, for gasoline, this is not the case. For a small fire you can use dry chemical CO2, water spray, or foam. If there is a spill or leak the first thing you do is eliminate all ignition sources. Ground any equipment you are using. Don't walk through the leak. Try to plug it if possible. Don't let it run into creeks, sewers, or other water sources. There is also a section on first aid. You need to get this right because what's good to aid for one chemical may be deadly for another. In this case, move the person upwind to fresh air. Remove and isolate any contaminated clothing and shoes.
All this sounds like common sense, but gasoline is something that we are around a lot and know about. Start looking at the trucks that go by, or at the placards near buildings. Do you recognize those? Learn what they are and what the safety measures are. If you are in the city and something goes wrong, this may be another tool in your tool kit for where it's safe and where it isn't.