Flammable liquids pose significant risks during storage and transport. This article explains the legal requirements (ADR, IMDG, IATA) and practical hazards and shows how the correct UN-certified packaging prevents incidents.
Summary of this article
Flammable liquids in ADR class 3, including substances with UN 1203 (petrol), UN 1993 (flammable liquids n.o.s.), UN 1263 (paint), UN 1170 (ethanol), UN 1219 (isopropanol), UN 1223 (kerosene) and UN 3295 (hydrocarbons), are used in virtually all industrial chains. They are found in production processes, maintenance applications, laboratories, high-tech assembly and logistics activities. Because they are used so frequently, it is easy to assume that the risks are manageable, but incidents in practice prove the opposite. Many flammable liquids have a low flash point, quickly develop volatile vapours and can immediately form a flammable atmosphere in the event of a leak. This makes it extremely important to package and transport them safely.
The relevance of this topic is reinforced by the fact that a significant proportion of incidents involving hazardous substances are caused by leaking or incorrectly classified packaging. Numerous inspections have shown that packaging is not suitable for the specific liquid, or that labelling and documentation do not comply with international transport regulations. This increases the risk of vapour accumulation, fire, explosion or environmental damage. Transporters, terminals and enforcement agencies are becoming increasingly strict in their checks. If a shipment does not comply with ADR, IMDG, ICAO-TI or IATA-DGR, it may not be transported, leading to delays, additional costs and sometimes administrative sanctions.
Flammable liquids are classified into three packaging groups that determine the level of danger. Packaging groups II and III are most common in industrial chains and are most often incorrectly packaged in practice, because many substances are considered everyday and relatively harmless. These include common solvents, coatings, alcohols and fuels, which can quickly cause a flammable situation in the event of leakage or vapour production, especially in the presence of heat, vibrations or unsuitable packaging materials.
For companies, this means that packaging is not a logistical afterthought, but a critical factor in their safety and compliance policy. The wrong choice of packaging materials or UN approval marks can have direct consequences for business continuity, damage claims or occupational safety. International regulations therefore prescribe detailed requirements for packaging construction, test methods such as drop tests and leak tests, marking, labelling and the administrative documentation that must accompany a shipment.
Organisations seek assurance that their packaging demonstrably complies with these regulations and that it can withstand the pressure build-up, mechanical stress and temperature variations that can occur during transport. The combination of legal obligations and practical risks explains why the demand for expert support in the safe packaging and transport of flammable liquids is growing rapidly.
Flammable liquids classified under ADR Class 3 are characterised by their low flash points, volatile vapours and ability to easily form a flammable atmosphere. Substances in Packing Groups I, II and III vary in volatility and flammability, but share one common characteristic: as soon as the liquid or its vapours come into contact with an ignition source, combustion or an explosive situation may occur. The hazards increase significantly when the liquid is under pressure, evaporates rapidly or reacts with the packaging material.
The greatest risks arise from leakage, damage to the packaging or exposure to heat. Many liquids produce vapours that are heavier than air and accumulate in low-lying areas such as cargo spaces, pits or warehouse floors. When these vapours reach a concentration between the lower and upper explosive limits, a minor ignition source—such as static electricity, a spark from a tool or a hot engine—may be sufficient to cause an explosion. These risks have been extensively documented in incident analyses, in which vapour dispersion and inadequate ventilation are frequently identified as contributing causes.
Pressure build-up also presents a significant hazard. When flammable liquids are exposed to higher temperatures, the internal pressure inside the packaging can rise rapidly. This may cause the packaging to rupture, deform or even burst open. A sudden failure can result in a combination of splashing, rapid vaporisation and the formation of a potentially life-threatening flammable vapour cloud.
Compatibility between the substance and the packaging is another factor that is often underestimated. Some liquids attack plastics or seals, causing microleaks to develop over time or reducing the structural strength of the packaging. This applies to certain solvents, alcohols and aromatic hydrocarbons, among other substances. Selecting an unsuitable material may result in the gradual release of vapours, corrosion of metal closures and interaction between the substance and the packaging material, further increasing the risk of failure.
The consequences of such incidents can be severe. Fires and explosions may lead to serious injuries, damage to buildings and installations, contamination of soil and water, and prolonged business interruption. Companies may also be held liable if their packaging, labelling, marking or documentation is found not to comply with international regulations such as ADR, IMDG, ICAO-TI/IATA-DGR, RID and ADN. Carriers and regulatory authorities such as the Dutch Human Environment and Transport Inspectorate (ILT) enforce these regulations strictly and may suspend shipments, impose fines or require goods to be repackaged. This not only causes costs and delays, but can also damage a company’s reliability and reputation.
Flammable liquids therefore require packaging that has been demonstrably proven to withstand the risks encountered during transport. Drop tests, leakproofness tests and pressure tests demonstrate whether packaging is sufficiently safe to prevent leakage and failure. Furthermore, many of these liquids may not be transported without valid UN certification and the correct application of that certification. Compliance with all applicable regulations is therefore not merely an administrative obligation, but an essential measure for safeguarding safety, business continuity and legal certainty.
The safe packaging and transport of flammable liquids from ADR class 3 requires the accurate application of international regulations and a thorough assessment of the properties of the substance in question. The requirements differ per UN number, per packaging group and per mode of transport, making it essential to interpret all relevant regulations correctly. The basis is laid down in the ADR for road transport, the IMDG Code for sea transport, the ICAO-TI and IATA-DGR for air transport, the RID for rail transport and the ADN for inland waterway transport. These regulations describe, among other things, which packaging is permitted, which UN marks are required and which additional conditions apply to temperature, pressure, marking and documentation.
Within ADR class 3, flammable liquids are divided into three packaging groups. The classification determines the requirements for packaging construction, test level and UN approval. In short:
The classification is determined by characteristics such as flash point, boiling point and additional physical-chemical properties. Packaging approved for PG I may be used for PG II and PG III, but packaging for PG III may never be used for substances in PG II or PG I. An incorrect choice will immediately lead to non-compliance with ADR and may be considered a violation by the authorities.
Determining the correct packaging starts with an analysis of the substance properties. These include vapour pressure, viscosity, compatibility with materials, temperature sensitivity and volatility. Many flammable liquids can attack plastic seals, corrode metals or generate excess internal pressure when heat is generated. Therefore, the packaging must be designed to withstand mechanical stress, pressure build-up and vapour generation. For many substances, additional conditions apply, such as temperature control during transport, ventilation restrictions or requirements for inner packaging when the liquid is particularly volatile.
UN-approved packaging must be demonstrably tested in accordance with the UN Manual of Tests and Criteria. The relevant tests include the drop test, the stacking test, the leak test and the hydraulic pressure test. These tests check whether packaging can withstand shocks, stress and pressure during transport and storage. The test level depends on the packaging group for which the packaging is approved. Only packaging that successfully passes all tests receives a valid UN approval mark. This approval mark consists of a combination of numbers, letters and codes that indicate for which substances, packaging group, material type and density factor the packaging is approved. Correct interpretation and application of this mark is crucial, as incorrect marking is a common cause of transport refusals.
In addition to physical packaging, marking, labelling and documentation play an equally important role. Every shipment of flammable liquids must be provided with the correct Class 3 hazard label, the correct UN number marking and clear mandatory texts where necessary. The transport document must also contain all the information prescribed in ADR 5.4, including the full transport name, package details, class, packaging group and any special provisions. Errors in documentation often result in fines, delays or repackaging obligations.
Finally, companies must take modal differences into account. Air transport places significantly stricter demands on packaging due to pressure and temperature fluctuations in the cabin. Sea freight requires extra attention to corrosion, moisture and long-term storage in containers. Inland waterway and rail transport have additional regulations for stability, ventilation and loading procedures. Without an understanding of these modality-specific differences, there is a risk that packaging will comply with ADR but not with IATA-DGR or IMDG, which will still make shipments impossible.
At Faes, we guide you through the entire process of safely and certified packaging of flammable liquids from ADR class 3. This ensures you of a solution that demonstrably complies with international transport regulations such as ADR, IATA-DGR, IMDG, RID and ADN, and that can withstand the physical and chemical stresses of storage and transport in practice. Our approach consists of four key steps that together ensure safety, efficiency and compliance with all legal requirements.
Together with the customer, we identify all relevant product and transport characteristics. We analyse the specific properties of the liquid, including UN number, packaging group, flash point, viscosity, vapour pressure, temperature sensitivity and compatibility with packaging materials. We also assess the conditions during transport, such as temperature fluctuations, vibrations and pressure differences. We then determine which UN certification applies and which additional requirements apply to air, sea or road transport. This analysis forms the basis for the design and the required test procedures in accordance with the applicable standards.
Our engineers translate the technical and legal requirements into packaging that meets all safety and certification requirements for flammable liquids. We consider the choice of materials, construction, pressure resistance, leak tightness and internal stabilisation. If necessary, we integrate absorbent materials or secondary containment solutions into the packaging to minimise risks such as leakage, pressure build-up and vapour formation. Insights from previous test series and practical experience are directly incorporated into the design, so that the packaging not only meets the required UN test level, but can also be used efficiently in daily logistics processes.
Faes works with recognised testing bodies to have the packaging validated according to the international test methods set out in the UN Manual of Tests and Criteria. We take care of all coordination with the test laboratory, ensure the correct configuration of all packaging and provide the necessary documentation, including technical specifications, test reports and certification files. The mandatory tests, such as drop tests, leak tests, stacking tests and hydraulic pressure tests, objectively demonstrate that the packaging meets the requirements for the safe packaging of dangerous liquids from the relevant packaging group.
After the testing process, we analyse the results and discuss them with the customer. Where optimisation is possible, we adjust design details or material choices so that the packaging not only complies with the standard, but also performs robustly and reliably in practice over the long term. If desired, additional iterations can be carried out to further improve performance, durability or handling.
This structured approach enables us to deliver packaging solutions that comply with international safety standards and are practical for use in complex supply chains. Faes combines technical certainty with operational reliability to ensure the safe and compliant transport of flammable liquids.
Do you want to be sure that your flammable liquids are transported safely, certified and in accordance with the relevant regulations?
Then contact Faes for a no-obligation consultation. Our specialists will be happy to help you with a tailor-made solution, from design to certification and logistical implementation.
Tim van de Puttelaar is the Engineering Manager at Faes and specializes in packaging engineering and custom solutions. In his articles, he shares insights on optimization, testing, and engineering projects that contribute to more efficient and sustainable packaging solutions within complex supply chains.
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