Hazard Classification of Desensitized Explosives for International Logistics
Abstract
This article outlines the dual classification system for desensitized explosives under both the UN Model Regulations for the transport of dangerous goods (TDG) and the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). It details the transport entries and the GHS classification methodology based on the corrected burning rate.
1. Introduction
Desensitized explosives are substances or mixtures which have been physically or chemically treated (e.g., wetted or diluted) to suppress their explosive properties so that they do not meet the criteria for inclusion in Class 1 (Explosives). Their safe use requires ensuring the stability of the desensitizing agent to prevent increased risk due to evaporation or leakage during storage and transport.
2. Transport Hazard Classification (per UN TDG)
According to the UN TDG and derived regulations (e.g., IMDG Code, IATA DGR), desensitized explosives are classified by physical state:
- Solid desensitized explosives: Assigned to Division 4.1 (Flammable solids). Corresponding UN entries include UN 1310, UN 3376, UN 3380, among others. Most require Packing Group I.
- Liquid desensitized explosives: Assigned to Class 3 (Flammable liquids). Corresponding UN entries include UN 1204, UN 3379, etc.
There are 41 relevant entries in the Dangerous Goods List. During transport, they must be kept out of direct sunlight, stored in a cool, well-ventilated place, and away from all heat sources.
3. GHS Hazard Classification and Test Method
The GHS provides quantified hazard criteria for desensitized explosives, classifying them into four categories based on the corrected burning rate (Ac):
| Category | Corrected Burning Rate (Ac) |
|---|---|
| Category 1 | Ac ≥ 300 kg/min but ≤ 1200 kg/min |
| Category 2 | Ac ≥ 140 kg/min but < 300 kg/min |
| Category 3 | Ac ≥ 60 kg/min but < 140 kg/min |
| Category 4 | Ac < 60 kg/min |
The specific test procedure and calculation method are prescribed in Part III, Section 51 of the UN Manual of Tests and Criteria. The corrected burning rate (Ac) is determined via a burning rate test (external flame application).
4. Classification Flowchart
The classification involves a logical decision process, typically starting with determining if the substance meets the definition, followed by exclusion tests per TDG, and finally the GHS burning test to assign the specific category. The detailed flowchart from the Manual of Tests and Criteria should be followed.
5. References
- United Nations. (2023). Recommendations on the Transport of Dangerous Goods: Model Regulations (ST/SG/AC.10/1/Rev.23).
- United Nations. (2023). Manual of Tests and Criteria (ST/SG/AC.10/11/Rev.8).
- International Maritime Organization. (2022). International Maritime Dangerous Goods (IMDG) Code.
- United Nations. (2023). Globally Harmonized System of Classification and Labelling of Chemicals (GHS) (ST/SG/AC.10/30/Rev.10).
Key Takeaway for Shippers & Buyers: Desensitized explosives are subject to dual classification: transport classification under UN TDG (Division 4.1 for solids, Class 3 for liquids) and GHS hazard categorization based on corrected burning rate (Ac). Proper identification and documentation are essential for safe and compliant international logistics.
Critical Reminder for Global Buyers Sourcing from China: When importing desensitized explosives or products containing such substances, always request the corrected burning rate (Ac) test report and verify the correct UN number (e.g., UN 1310, UN 3376, UN 3380, UN 1204, UN 3379) with your freight forwarder. Misclassification can lead to severe transport incidents and regulatory penalties.