All About Class Two Gases

Haz Guides Jun 28, 2020

In this guide we'll be covering dangerous goods class two explosives in depth.

What is a Class Two?

You may need to break out your chemistry degree for this one. Goods under this class are substances which at 50ºc have a vapor pressure of 300kPa or is completely gaseous at 20ºc at standard atmospheric pressure.

All gasses that are pressurized for shipment, even if they aren't poisonous or flammable, are considered class two dangerous goods. Some things that fall under this class are oxygen, propane, aerosol containers, helium, and more.

Class Two Divisions

Dangerous goods class two gasses are broken up into three divisions depending on specific danger of the gas.

2.1 These are flammable, non-toxic gasses. Meaning they are ignitable at 101.3 kPa when in a mixture of 13% or less by volume with air; or has a flammable range at 101.3 kPa with air of 12% or greater regardless of lower limit; or is determined to be flammable in accordance with ASTEM E681-85.

And, if shipping aerosol, it must be assigned to this division if the contents include 85% flammable components or more by mass and the chemical heat of combustion is 30 kJ/g more more; or if the aerosol is deemed flammable per UN Manual of Tests and criteria for flammability.

Some gasses include acetylene, hydrogen, and propane.

2.2 These gasses are non-flammable and non-toxic gas. This division includes compressed gasses, compressed gasses in solution, liquefied gasses, pressurized cryogenic gasses, and more. A non-flammable gas is one that exerts in packaging an absolute pressure of at least 280 kPa at 20ºc and does not meet the definition of either other divisions.

Aerosols are assigned to this dangerous goods division when the contents mass are 1% or less flammable and the heat combustion is less then 20 kJ/g.

2.3 These are gasses that are toxic and poisonous by inhalation. They are considered division 2.3 when the material is a gas at 20ºc or less and a pressure of 101.3 kPa where the material is known to be so toxic to humans as to pose a hazard to health during transportation, or; is presumed to be toxic to humans because when tested on laboratory animals had an LC50 value of not more than 5000 ml/m3.

Examples of these are fluorine gas and chlorine gas.

Class Two Dangerous Good Label

The label for a class tow gas is different depending on the division. Flammable gasses (2.1) are red, non-flammable gasses are green (2.2) or yellow if oxygen (alternate placard), and a white with skull and cross bones and "inhalation hazard" for toxic gasses (2.3).

Dangerous goods class two placards

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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