Which of the following is true about identifying materials by placard numbers?

• A. Toxic gases are identified by placard number 2.3
• B. Flammable liquids are identified by placard number 2.1
• C. Corrosive liquids are identified by placard number 1.3
• D. Radioactive materials are identified by placard number 4.5

Answer: (A)

Placard numbers identify hazard class and subdivision, so you can quickly recognize the exact type of material you’re dealing with. The first number shows the hazard class, and the number after the decimal points to a specific division within that class. For gas hazards, class 2 covers gases, and the subdivisions include 2.1 for flammable gases, 2.2 for non-flammable, non-toxic gases, and 2.3 for toxic gases. That’s why placing a toxic gas under 2.3 is the correct match.

Flammable liquids aren’t identified by 2.1 because that subdivision is for flammable gases, not liquids; flammable liquids fall under class 3. Corrosive liquids are class 8, not 1.3, and radioactive materials are class 7, not 4.5.