Hazardous Materials Identification and Recognition
This domain tests whether you can establish what the material is, how much is present, and which hazards apply before committing anyone. Questions typically supply several clues, one or two of them misleading, and ask for the most reliable next identification step.
What each clue actually tells you
- Container and occupancy. Shape narrows the product: MC-306/DOT-406 elliptical tanks carry flammable liquids, MC-331 carries propane, DOT-117 tank cars carry flammable liquids, ton containers carry chlorine. Occupancy (paint booth, plating shop, farm supply) suggests a product family.
- UN number and proper shipping name. The four-digit UN number in 49 CFR 172.101 is the identifier; the proper shipping name follows it on shipping papers and markings.
- Placards and labels. Placards are required at 1,001 lb aggregate gross weight for Table 2 materials and any quantity for Table 1; labels mark nonbulk packages. Both convey hazard class, not a unique chemical.
- Shipping papers. Proper shipping name, class, UN number, quantity, and a 24-hour emergency telephone number are required.
- SDS. At fixed facilities, 29 CFR 1910.1200(g) requires a 16-section SDS giving physical properties, reactivity, and PPE guidance.
- ERG. Yellow pages index by UN number, blue by name, orange guides give hazards and isolation, green tables give isolation and protective action distances.
- Instruments. Four-gas meters, PIDs, colorimetric tubes, pH paper, and radiation meters each have cross-sensitivity and range limits.
Rules that score marks
- Corroborate at least two independent clues before naming a product.
- A placard gives class and UN number; never read the class digit as the identification number.
- Empty or residue packaging still carries the hazard.
Worked example
A tanker is placarded UN 1203, FLAMMABLE, with a 3 in the lower corner. Reasoning: the four-digit number identifies gasoline; the 3 is the hazard class, not the ID. The elliptical tank confirms a flammable liquid. ERG Guide 128 confirms water-immiscible flammable liquid hazards and directs you to the green table for UN 1203 isolation distances. You then confirm quantity and shipping name from the shipping papers and note properties: flash point about -45 F, LEL 1.4 percent, vapor density 3 to 4, so vapors travel downhill and downwind to ignition sources.
Traps
- Reading the placard class number as the UN number.
- Treating an EMPTY placard as no hazard.
- Assuming a specific chemical from a guide number that covers a whole class.
- Ignoring railcar or container type when the placard and the tank shape disagree.