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TDG: The nine classes and their divisions

All nine classes of dangerous goods and their divisions, from Class 1.1 explosives to Class 9 miscellaneous goods, the criteria that place a substance in each class, and what Packing Groups I, II and III mean.

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The nine classes and their divisions · Question 1Score 0/0

Medical laboratory samples that could cause disease are in which division?

Study reference: TDG Act and Regulations (current to 2026-09-30), Ch. 2 Classes and divisions — Part 2, ss. 2.9–2.45

All 15 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

  1. Medical laboratory samples that could cause disease are in which division?

    1. Class 6.2
    2. Class 6.1
    3. Class 9
    4. Class 8

  2. Using the closed-cup method, a liquid's flash point is at or below what temperature for it to fall in Class 3?

    1. 23 °C
    2. 60 °C
    3. 35 °C
    4. 93 °C

  3. In which packing group are all Class 1 explosives placed?

    1. Packing Group III
    2. Packing Group I
    3. No packing group at all
    4. Packing Group II

  4. A flammable liquid boils at 80 °C and has a flash point of 15 °C. Which packing group applies?

    1. Packing Group III
    2. Packing Group II
    3. Packing Group IV
    4. Packing Group I

  5. What is the difference between Class 5.1 and Class 5.2?

    1. 5.1 is toxic substances; 5.2 is infectious substances
    2. 5.1 is oxidizing substances; 5.2 is organic peroxides
    3. 5.1 is flammable solids; 5.2 is water-reactive solids
    4. 5.1 is compressed gases; 5.2 is refrigerated gases

  6. A gas is neither flammable nor toxic and is shipped at 300 kPa absolute at 20 °C. Which division is it?

    1. Class 2.4
    2. Class 2.2
    3. Class 2.3
    4. Class 2.1

  7. What does Packing Group I indicate?

    1. Medium danger
    2. Great danger
    3. No danger in transport
    4. Minor danger

  8. A flammable liquid boils at 30 °C. Which packing group applies?

    1. Packing Group I
    2. It depends only on the flash point
    3. Packing Group II
    4. Packing Group III

  9. A pyrophoric material catches fire within minutes of touching air. Which class is it in?

    1. Class 4.3
    2. Class 4.1
    3. Class 2.1
    4. Class 4.2

  10. Which Class 1 division describes explosives with a mass explosion hazard?

    1. Class 1.6
    2. Class 1.2
    3. Class 1.4
    4. Class 1.1

  11. Which gases belong in Class 2.3?

    1. Gases that contain oxygen and feed a fire
    2. Gases that are shipped as refrigerated liquids
    3. Gases known to be toxic or corrosive to humans
    4. Gases that ignite in a 13% mixture with air

  12. What does Class 1.4 mean for an explosive?

    1. A very insensitive substance with a mass explosion hazard
    2. No significant hazard beyond the package if it ignites
    3. A projection hazard but not a mass explosion hazard
    4. A mass explosion hazard that affects the whole load

  13. Which class has neither divisions nor packing groups?

    1. Class 1, explosives
    2. Class 7, radioactive materials
    3. Class 5, oxidizers and peroxides
    4. Class 3, flammable liquids

  14. A substance gives off flammable gas when it gets wet. Which division covers it?

    1. Class 4.2
    2. Class 5.1
    3. Class 4.3
    4. Class 4.1

  15. An asphalt-free liquid that is not otherwise dangerous is shipped at 120 °C. Which class can it fall into?

    1. Class 9, because it is carried hot
    2. Class 8, because heat can corrode
    3. Class 3, because it is a liquid
    4. It is not dangerous goods at all

The nine classes and their divisions: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Class 1, Explosives (ss. 2.9–2.12)

  • Class 1 covers substances that can produce gas by chemical reaction fast and hot enough to damage the surroundings, and articles designed to give an explosive or pyrotechnic effect.
  • Class 1 has six divisions: 1.1 mass explosion hazard; 1.2 projection hazard without mass explosion; 1.3 fire hazard with only a minor blast or projection hazard; 1.4 no significant hazard beyond the package; 1.5 very insensitive substances with a mass explosion hazard; 1.6 extremely insensitive articles with no mass explosion hazard.
  • Explosives are sorted into 13 compatibility groups, shown by a letter after the division (for example 1.4S).
  • Explosives are always in Packing Group II.

Class 2, Gases (ss. 2.13–2.14)

  • Class 2 includes gases, mixtures of gases, articles charged with a gas and aerosols.
  • Class 2.1 Flammable Gases ignite in a mixture of 13% or less by volume with air, or have a flammability range of at least 12 percentage points.
  • Class 2.2 Non-flammable and Non-toxic Gases are carried at an absolute pressure of at least 280 kPa at 20 °C, or as refrigerated liquids, and are not in 2.1 or 2.3.
  • Class 2.3 Toxic Gases are known to be toxic or corrosive to humans, or have an LC50 of 5 000 mL/m³ or less.
  • Aerosols are shipped under UN1950, AEROSOLS.

Class 3, Flammable Liquids (ss. 2.18–2.19)

  • A liquid is in Class 3 if its closed-cup flash point is 60 °C or less, or if it is carried at or above its flash point.
  • Packing Group I: initial boiling point 35 °C or less. Packing Group II: boiling point above 35 °C and flash point below 23 °C. Packing Group III: everything else in Class 3.

Class 4 (ss. 2.20–2.21)

  • Class 4.1 Flammable Solids: readily combustible solids, solids that can cause fire through friction, desensitized solid explosives, self-reactive and polymerizing substances.
  • Class 4.2 Substances Liable to Spontaneous Combustion: pyrophoric substances that ignite within 5 minutes of contact with air, and self-heating substances.
  • Class 4.3 Water-reactive Substances: substances that give off flammable gas on contact with water at more than 1 L per kg per hour, or ignite in the test.

Class 5 (ss. 2.23–2.24)

  • Class 5.1 Oxidizing Substances yield oxygen and so cause or feed the combustion of other material.
  • Class 5.2 Organic Peroxides are thermally unstable organic compounds with the -O-O- structure; they can decompose in a self-accelerating way.

Class 6 (ss. 2.26–2.28, 2.36)

  • Class 6.1 Toxic Substances can cause death, serious injury or harm to health if swallowed, inhaled or absorbed through skin.
  • Oral toxicity puts a substance in 6.1 when its oral LD50 is 300 mg/kg or less; dermal toxicity when the dermal LD50 is 1 000 mg/kg or less.
  • Class 6.2 Infectious Substances are split into Category A (can cause permanent disability or life-threatening disease on exposure) and Category B.

Classes 7, 8 and 9 (ss. 2.37–2.45)

  • Class 7 is radioactive material as defined in the Packaging and Transport of Nuclear Substances Regulations, 2015; it has no divisions and no packing groups.
  • Class 8 Corrosives destroy the full thickness of human skin, or corrode steel or aluminium faster than 6.25 mm a year at 55 °C.
  • Class 8 has no divisions; if a substance is known to be corrosive from published evidence and is not tested, it goes in Packing Group I.
  • Class 9 covers miscellaneous products, substances or organisms, such as marine pollutants and goods carried hot (liquids at 100 °C or more, solids at 240 °C or more).
  • Class 9 has no divisions and is Packing Group III unless Schedule 1 shows otherwise.

Packing group

  • The packing group reflects inherent danger: PG I great danger, PG II medium danger, PG III minor danger.
  • On documents the packing group is written as a Roman numeral (I, II or III).

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