Class 4 - Division 4.3

Division 4.3 is for substances that are dangerous when wet. When these substances interact with water, they are liable to become spontaneously flammable or to give off flammable gas in dangerous quantities. Mixtures of these substances are easily ignited by all ordinary sources of ignition, such as sparks.

During testing described in the "UN Manual of Tests and Criteria," Part III, Subsection 33.4.1., substances are assigned to Division 4.3 if spontaneous ignition takes place during any step of the procedure or if there is an evolution of a flammable gas at a rate greater than 1 L/kg of the substance per hour. The test method can apply to solids and liquids, but it does not apply to pyrophoric substances. The substance must be tested at an ambient temperature when it comes in contact with water.

Assignment to packing groups is as follows:

• Division 4.3 substances are assigned to Packing Group I if they react vigorously with water at ambient temperatures, and if they demonstrate a tendency for the gas produced to ignite spontaneously.
• Substances are assigned to Packing Group II if they do not meet the criteria for Packing Group I and they react readily with water with a rate of flammable gas evolution that is equal to or greater than 20 L/kg.
• Substances are assigned to Packing Group III if they do not meet the criteria for Packing Group I or II and they react slowly with water with a rate of flammable gas evolution that is greater than 1 L/kg.

Examples of Division 4.3 dangerous goods include:

• Alkaline earth metal alloys
• Aluminum powder, uncoated
• Calcium
• Calcium carbide
• Calcium hydride
• Lithium
• Magnesium
• Sodium

Organometallic compounds contain a bond between carbon and a metal. These substances may be classified as Division 4.2 or 4.3, depending on their properties. Refer to the flowchart in Figure 2.4.2 of the "UN Recommendations on the Transport of Dangerous Goods." These dangerous goods include UN 3392 through UN 3397.

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