Hazardous Classes

Haz Guides Jun 24, 2020

Welcome back to the world of HazMat shipments!

In this guide we'll be covering the different classes of hazardous cargo and what regulations apply to each of them. Yes, there will be a little law and regulation in here but, we'll make it through and it might even be a little fun.

The Classes

Hazardous materials or dangerous goods are broken up into different classes depending on their make up and the characteristics that make them dangerous. If you remember from the intro, the materials are determined to be hazardous or dangerous depending on their potential to impact health, safety, environment, or property when transported. These classes have been adopted by the UN across the globe so that each country is the same when it comes to what materials are considered dangerous or hazardous and what rules apply.

The materials are broken up into 9 classes and then divisions from there.

  1. Explosives
  2. Gasses
  3. Flammable and Combustible Liquids
  4. Flammable Solids
  5. Oxidizing Substances, Organic Peroxides
  6. Toxic Substances and Infectious Substances
  7. Radioactive Material
  8. Corrosives (Liquids and Solids)
  9. Miscellaneous Hazardous Materials
Photo by Le Kiet / Unsplash

Class 1 - Explosives

Class one explosives are materials that can rapidly detonate after a chemical reaction. Think ammunition & fireworks. This class is broken down into six more divisions.

1.1 Materials or substances that have a mass explosion hazards.

1.2 Materials or substances that have a projection hazard but not mass explosion hazard.

1.3 Materials with a fire hazard  and either a minor blast hazard or minor projection hazard.

1.4  Materials with no significant hazard, only a small hazard in the event of ignition during transportation with any effects largely confined to the package.

1.5 Very intensive materials with a mass explosion hazard.

1.6 Extremely intensive articles without a mass explosion hazard.

PA Coal Power Plant - steam network
Photo by Martin Adams / Unsplash

Class 2 - Gasses

Class two covers gasses, compressed, liquefied, refrigerated, dissolved, and aerosols, as well as articles containing gas. Like natural gas, propane, fire extinguishers, etc.  Gasses are broken up into 3 divisions and they are relatively simple.

2.1 Flammable gasses

2.2 Non-flammable, non-toxic gasses

2.3 Toxic gasses

Photo by Frantzou Fleurine / Unsplash

Class 3 - Flammable Liquids

Class three are liquids with a relatively low flashpoint (the temperature where the liquid gives off enough vapor to ignite) ~ 150f or 65c and lower. These are usually liquids that give off an odor or vapor in your everyday life like gasoline, diesel, paint, and acetones. This class also covers molten solids with flashpoints above 65c, but those aren't transported often. There are no divisions to this class.

Photo by Brett Jordan / Unsplash

Class 4 - Flammable Solids

Class four materials are solids that react with themselves or are combustible under normal environmental conditions - like a Note 7. These items can produce a strong exothermic reaction - giving off an immense about of heat when the material reacts with itself. Materials in this class include things like matches, metal like magnesium and metal powders, sulphur, batteries, and sodium. There are three divisions of class fours.

4.1 Flammable solids

4.2 Substances liable to spontaneous combustion

4.3 Materials that produce flames when mixed with water.

Photo by Etienne Girardet / Unsplash

Class 5 - Oxidizing Substances and Organic Peroxides

These are nasty buggers. These are materials that generate oxygen (which is extremely explosive on its own) after their chemical reaction. Materials you may have heard of include hydrogen peroxide, sodium nitrate, or ammonia fertilizers. There are two divisions to class fives.

5.1 Oxidizing substances

5.2 Organic peroxides

Clinical sample
Photo by National Cancer Institute / Unsplash

Class 6 - Toxic Substances and Infectious Substances

Class six is a relatively simple one. These are typically those items we learned as a kid and adolescence to be cautious around. Simply put, these are items that are toxic or infectious like lead compounds, cyanide's, cresol, pesticides, biological waste and clinical samples. There are two very simple divisions of class sixes.

6.1 Toxic substances

6.2 Infectious substances

I took a remote highway cutting through Idaho and stumbled upon a free roadside museum that used to be a nuclear power plant. Obviously, I had to check it out and add another hour to my drive... Here's a bunch of cool 1950s-era dials and knobs located on the main control station.
Photo by Dan Meyers / Unsplash

Class 7 - Radioactive Material

Queue the panic - it's radioactive material time. Every time these shipments move, everyone involved makes a lot of noise - for understandable reasons. While worry is understandable - health and safety are always a top priority - these shipments are always contained in a special type of container that limits the emitted radiation. Some of the items that move under this class are enriched uranium, medical equipment, radioactive ore, or even waste. We'll dig into this class (and all others) in coming sections.

Photo by Who’s Denilo ? / Unsplash

Class 8 - Corrosive Substances

Class eight materials are the type that will severely damage a surface if they come in contact. An example of this would be an acid, where it will dissolve whatever it comes in contact with. Batteries and battery fluid usually fall into this category as well. Class eight does not have any divisions.

Photo by Jonathan Borba / Unsplash

Class 9 - Miscellaneous Dangerous Goods

The everything else pile.

Class nines are those items that don't quite fit in the other classes but still present a hazard to health, the environment or property. Typically these are items that can cause a potential for environmental harm or are marine pollutants like lithium ion batteries, zinc, auto motors, and more. There are no class divisions for class nines.


That wraps up an over view of the hazard classes and their divisions. Over the next couple of guides, we'll be posting about the specifics of each class and the placarding required for them.

Nick Seferos

Sea-going maritime professional on ships and tugs turned to shore-side terminal life. Nick manages shore-side personnel and security, customs, and hazardous shipments in a container terminal.

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