Epichlorohydrin (1-chloro-2,3-epoxypropane; CAS 106-89-8) moves through bulk and packaged supply chains as UN 2023, Class 6.1 (3), PG II. The same entry appears in ADR Table A, RID Table A, ADN Table A, the IMDG Code Dangerous Goods List, ICAO Doc 9284, and 49 CFR §172.101; the classification is therefore applied across road, rail, inland waterway, marine, and air modes without modal downgrading. The physical data that define this dual-hazard entry are liquid density 1.18 g/cm³ at 20 °C, vapour pressure 1.66 kPa at 20 °C, closed-cup flash point 31 °C, boiling point 115 °C at 101.3 kPa, and vapour density approximately 3.2 relative to air. Because the vapour is heavier than air, leak detection in packaged cargo holds, road tanker sumps, and rail tank car pits concentrates at low points, and mechanical ventilation must be directed at floor level rather than roof level.

Commercial ECH is consumed principally in liquid epoxy resin synthesis, synthetic glycerine production, epichlorohydrin elastomers, water-treatment resins, and paper wet-strength resins. These downstream operations receive the material as a high-purity oxirane and unload it into closed storage systems. The transport classification is not a peripheral label; it determines tank materials, pressure relief settings, stowage segregation, crew exposure controls, and emergency response. The hazard profile is shaped by the chloromethyloxirane ring, which is an alkylating electrophile. That chemical behaviour produces both acute toxicity and a tendency to undergo exothermic ring-opening reactions if contaminated with acids, bases, or metal halides.

Why Does the UN Model Regulations Assign Primary Class 6.1 When the Material Is Flammable?

The primary hazard is toxic inhalation. In UN Model Regulations Chapter 2.6, a vapour with a 4-hour LC50 greater than 0.5 mg/L and less than or equal to 2.0 mg/L is placed in Class 6.1 Packing Group II. Published acute inhalation data for epichlorohydrin fall within this band. The oral LD50 in rats of approximately 90 mg/kg and the dermal LD50 in rabbits reported near 250 mg/kg would not by themselves require the same packing group, but the vapour endpoint controls the transport assignment. This is operationally significant: a spill does not behave like a simple solvent release because the vapour can cause systemic injury at concentrations below the conventional odour warning, and full-face respiratory protection with an organic-vapour cartridge or supplied air is used during transfer.

The subsidiary Class 3 hazard is based on the closed-cup flash point of 31 °C. Under the Class 3 criteria in UN Model Regulations Chapter 2.3, a liquid with a flash point of at least 23 °C and not more than 60 °C falls into Class 3 Packing Group III. UN 2023 carries the subsidiary risk as Class 3, while the Packing Group II applies only to the primary Class 6.1 assignment. At 20 °C the vapour pressure is 1.66 kPa, and the vapour can produce flammable mixtures in ullage spaces; however, the toxic hazard is treated as controlling because the inhalation toxicity threshold is reached at lower concentrations than the lower flammable limit.

Under the European harmonised classification in Annex VI of Regulation (EC) No 1272/2008, ECH carries Flam. Liq. 3 H226, Acute Tox. 3 H331, Skin Corr. 1B H314, Skin Sens. 1 H317, and Carc. 1B H350. These supply-side labels are distinct from transport classification but align with the same toxicological endpoints. The transport classification remains governed by the UN Model Regulations, and the UN 2023 entry is the binding description for shipping papers, placards, and modal segregation decisions.

Packaging instruction P001 in UN Model Regulations Chapter 4.1 governs UN 2023 liquids in single and combination packagings. Because the material is a chlorinated ether, closure gaskets and inner coatings are qualified by compatibility testing, not merely by generic hydrocarbon resistance. Steel drums remain a common industrial package, while stainless steel or lined steel ISO tank containers are used for bulk lots. The inner packaging limits for combination packagings are specific to the material and packing group; the relevant P001 table, not the general Class 3 entry, controls the maximum capacity. Package performance tests follow the UN Model Regulations Chapter 6.1 requirements for drop, leakproofness, and stack performance. For limited quantities, the assigned dangerous goods list value must be checked because the Class 6.1 PG II toxic inhalation profile restricts the inner packaging size below the default PG II liquid allowance in many modal variants.

Rail Tank Car and ISO Tank Container Loading Practice

Bulk loading racks for ECH use bottom loading with closed vapour recovery. The displaced vapour is routed to a thermal oxidizer or scrubber because it contains toxic chlorinated species and a flammable fraction. Nitrogen padding is used to keep the vapour space inert when tanks are stored or in transit; standard practice is to maintain a low positive pressure, typically between 20 kPa and 50 kPa gauge, after loading. The exact setpoint derives from the tank-certified maximum allowable working pressure and the loading terminal pressure-drop calculation. Rail tank cars in ECH service require pressure relief devices set below the tank test pressure and arranged to prevent direct discharge to the walking surface during loading. Bottom outlet valves, where fitted, must meet the closure protection requirements of the applicable tank specification; many ECH cars are equipped with external bottom outlet ball valves and cap assemblies.

Transfer pumps are selected for low-shear diaphragm or canned-motor designs to minimize heat input. The liquid viscosity at 20 °C is approximately 1.03 mPa·s, so the pumping head loss in 80 mm stainless steel lines is manageable; however, dead legs and filter housings can hold stagnant liquid that absorbs moisture from humid air. Loaded lines are therefore pigged and blown with dry nitrogen until the outlet dew point is below -20 °C. Field experience on marine terminal hose racks shows that stagnant ECH in a carbon-steel manifold under humid conditions can form a viscous oligomeric layer within 24–72 h, increasing differential pressure across pump strainers and requiring manual cleaning.

Marine Vessel Cargo Tanks Are Operated Under Closed Loading and Vapour Return

Under the IMDG Code Dangerous Goods List, UN 2023 appears with Class 6.1, subsidiary Class 3, Packing Group II and emergency schedule EmS F-A, S-A. Packaged cargo on container ships must be stowed away from living quarters and segregated from strong acids, bases, oxidizers, and amines. Chemical tankers carrying ECH use stainless steel cargo tanks, closed gauging, and vapour return to the shore tank. The cargo tank relief system is set to prevent atmospheric release during normal closed transfers; in the event of fire exposure, relief flow is designed for the fire case in the vessel's IBC Code certificate. The primary incompatibility is with sodium hydroxide, because the dehydrochlorination reaction that epoxy resin plants use deliberately is exothermic and can self-accelerate if the two liquids mix in a confined manifold. Segregation in packaged stowage follows the IMDG Code segregation table for Class 6.1 against Class 8, with special attention to alkalis and strong mineral acids.

Air freight forwarding of UN 2023 is the most restrictive mode. The combination of a Packing Group II inhalation endpoint and the Class 3 subsidiary risk removes the material from ordinary passenger baggage and most small-parcel express exceptions. Cargo acceptance must be confirmed against the current IATA Dangerous Goods Regulations dangerous goods table because passenger aircraft restrictions are mode-specific and can change with carrier policy. The inner packaging, absorbent, and outer packaging must meet the applicable ICAO Technical Instructions packing instruction for toxic liquids; pressure differential capability at cruising altitude is evaluated, and closures must withstand the internal vapour pressure at 55 °C. Packaging for air mode is not interchangeable with road mode simply because the UN number is identical. The vapour pressure at 20 °C is 1.66 kPa, but at elevated temperature the pressure increases; closures and outer packagings must be tested to the higher temperature condition in the air transport compliance regime.

The following compliance matrix summarizes the classification entry across the main modal instruments.

If a Shared Terminal Handles Sodium Hydroxide on the Adjacent Manifold

This is the highest-consequence contamination scenario in ECH terminals. Epichlorohydrin reacts with aqueous sodium hydroxide to form glycidol and sodium chloride; further reaction yields oligomeric glycol ethers and cross-linked resin. The reaction is exothermic and releases heat faster than the cooling capacity of small-diameter transfer lines. Shared manifolds are therefore either dedicated or designed with double block-and-bleed valves, removable spool pieces, and interlock systems that require line clearance before product changeover. A temperature rise above 50 °C in an ECH storage tank caused by contamination is a process-safety trip condition; operators initiate tank quench or transfer to a dump drum, depending on the facility design. Published data for this specific configuration is limited to facility risk assessments, but the chemistry is a standard epoxy synthesis reaction.

Spill response for UN 2023 follows Emergency Response Guidebook Guide 155. Full-ensemble vapour protection and positive-pressure self-contained breathing apparatus are used for large releases. The flammable component is controlled by removing ignition sources, but the toxic component requires diking and preventing entry into water. Use of sodium hypochlorite, alkaline cleaners, or amine-based neutralizers is prohibited in the spill area because these agents accelerate polymerization. Inert sorbents such as expanded mineral granules are specified; the absorbed waste must be packaged in UN-approved containers because the spent sorbent still carries the hazard of the original substance. Wash water from equipment cleaning is collected and routed to a permitted treatment system; discharge to storm drains is not acceptable without prior analysis for epichlorohydrin and its hydrolysis products.

Epoxy resin producers receiving UN 2023 in 25,000 L ISO tank containers connect a closed-loop nitrogen displacement system directly to the reactor feed line. The ECH is metered through a mass-flow meter into a bisphenol-A slurry under alkaline conditions; the process vessel operates under nitrogen and the vent is routed to a caustic scrubber. The same physical and toxicological properties that define the transport classification—vapour pressure 1.66 kPa at 20 °C, closed-cup flash point 31 °C, and primary Class 6.1 inhalation toxicity—govern the design of the receiving system. Transfer pumps, relief valves, and mechanical seals are rated for the material and for the maximum unloading temperature, and the transaction from transport container to reactor is executed without breaking containment.