By the way, there area number of other dangerous goods classes according to ADR,ranging from dangerous goods class 1 todangerous goods class 9.
In comparison, most classes (such asdangerous goods class 3) aremuch less extensive, which does not always make the optimal handling of dangerous goods class 4 easy – in case of doubt, the real substance must be considered here, as the supercategory may be too extensive for special requirements.
Subclasses of flammable solids
Like most other classes of dangerous goods, Class 4 is differentiated into furthersubclasses. These range from subclass 4.1 to subclass 4.2 to subclass 4.3 and are characterized by the following properties:
Subclass 4.1
Division 4.1 includes flammable solids that have self-reactive and desensitized explosive properties. They are considered highly flammable and can cause a fire just by a spark or friction. In addition, substances that decompose exothermically through contact with impurities or through exceptionally high temperatures also belong in this category.
Another important representative is explosive materials that have either been moistened with water or alcohol or contain sufficient plasticizing or inerting agents that the explosive properties are suppressed. Commonexamplesof mixtures and chemical substances in Division 4.1 include sulfur, matches, rubber residues, and aluminum powder. However, substances that meet the properties of Hazardous Materials Class 1, are organic peroxides, or have a heat of decomposition of less than 300 joules per gram are exempt.
Subclass 4.2
Division 4.2 containsspontaneously combustible substancesand includes both solid and liquid mixtures and solutions. The criterion is that the substance can ignite in contact with air within five minutes. Likewise, this category includes representatives that exhibit self-heating properties in contact with air, as these substances can ignite in larger quantities over a long period of time. Typical examples are white phosphorus, fish meal, coal, metallic iron or varnishes.
These so-called pyrophoric substances are additionally subdivided intodifferent packing groupsin Division 4.2, which makes identification easier in the event of damage. This also affects the specifications for storage. A distinction is made between packing group I (self-igniting), II (self-heating) and III (less self-heating).
Subclass 4.3
Third in the group is Division 4.3, which includes articles and substances which,in contact with water, emit flammable gases. In combination with air, this creates an explosive mixture. For some substances, the heat alone in the mixture-water reaction is already sufficient to cause ignition of the resulting gas.
Examples of subclass 4.3 include sodium, calcium, zinc powder and by-products from aluminum production. As with Division 4.2, additional packing groups are differentiated according to thedegree of hazard. For this subclass, these are packing group I (violent reaction), II (slight reaction) and III (slow reaction).
Problem in traffic
Especially in transport, dangerous goods class 4 offers some challenges that can quickly become problematic. Due to the self-decomposing, flammable or even explosive properties,attention must be paid to appropriate packaging for containers and means of transport: These must have ADR approval. In addition, legally mandatory labeling (for example, byGHS mark) and constant inspections apply.
In addition,standard equipmentmust be available for the transport of dangerous goods, which according to ADR must include, for example, high-visibility vests and warning triangles, suitable fire extinguishers, personal protective clothing, as well as a portable lighting device and load securing equipment. In addition, an ADR license is required for the truck driver.
Dangerous goods class 4 marking
For dangerous goods class 4,appropriate labelingmust be provided in transport so that it can be directly assigned which hazards emanate from the respective substances and mixtures. In particular, the GHS signs are decisive for this, but also the individual signs for subclasses 4.1 to 4.3. Both must be clearly visible on the containers as well as on the outside of the truck.
By the way, not every truck driver is allowed to transport dangerous goods. Instead, only those drivers who have obtained anADR license in an ADR training coursemay be used. They must also have special ADR equipment and have been instructed on what to do in the event of damage and the correct departure check.
Behavior in the event of damage
Due to the different properties of the individual goods in subclasses 4.1 to 4.3, the behavior in the event of damage is also not always the same. It is important toaddress the particular properties of the substancesand to consider some basic behaviors for flammable substances. The following overview can be considered as orientation:
- Division 4.1: If damage occurs with substances in this division, water must not be used for extinguishing. Otherwise, this could promote the explosive capabilities of the hazardous material.
- Division 4.2: Since the spilled hazardous material is self-igniting, special care must be taken. In the event of a cargo spill during transportation, not only should extreme care be taken, but a suitable dry chemical should also be used. Water must never be used for extinguishing.
- Division 4.3: Water is not suitable for extinguishing substances in this category. Instead, a special extinguishing agent must be used. These include, for example, special powder or dry sand. In the event of damage, be sure to keep corresponding hazardous substances away from sources of ignition.
Hazard class 4 is the most extensive hazard class
Dangerous goods class 4 is not only one of the mostcomprehensive representatives according to ADR, but also includes some substances that are frequently encountered in everyday life. In the three subclasses a) flammable solids, (b) substances liable to spontaneous combustion and (3c) substances which, in combination with water, form flammable gases, are grouped together.
Not least for this reason, it is elementary for storage and transport to rely onappropriate safety precautions, labeling and expertise. This is the only way to optimally meet the respective hazard characteristics.
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