For sulfuric acid buyers, the two compliance deadlines—China Hazchem Law and EU CLP 2026—do not run in parallel. The China obligation attaches to the first import transaction; the EU obligation attaches to a calendar cutoff. Concentrated sulfuric acid (CAS 7664-93-9, EC 231-639-5, UN 1830) and aqueous solutions of sulfuric acid must be classified, documented, and transported according to both jurisdictions. A buyer that treats the two deadlines as a single data update will be non-compliant in at least one territory.

What Changes on 1 May 2026 for Aqueous Sulfuric Acid Mixtures?

Commission Delegated Regulation 2023/707 inserted hazard classes for endocrine-disrupting properties for human health and the environment, PBT/vPvB, and PMT/vPvM into Regulation (EC) No 1272/2008. For substances, the operative date was 1 May 2025; for mixtures, the operative date is 1 May 2026. Sulfuric acid, an inorganic monoacid with no bioaccumulative parent structure, would not normally meet the PBT/vPvB or PMT/vPvM criteria. The same is generally true for endocrine disruption under current screening indicators. However, aqueous sulfuric acid entered into commerce as a diluted reagent or cleaning preparation is a mixture under CLP, and the 2026 date obliges the importer, formulator, or downstream user to review the full component list for substances that may introduce one of the new hazard classes. A 98% H₂SO₄ transfer handled as a pure substance is outside the 1 May 2026 mixture trigger, but any dilution with water creates a two-component mixture subject to the later deadline.

Safety data sheet updates must appear in Section 2.1, 2.2, and 2.3, with the new hazard classes and associated precautionary statements in Section 2.2. Where a formulated acid cleaner contains a nonionic surfactant classified as PMT, the SDS and label change even though sulfuric acid itself does not drive the new classification.

China Registration Triggers Before the First Import Declaration

China’s Catalogue of Hazardous Chemicals (2015 Edition) lists sulfuric acid with CAS 7664-93-9. Article 66 of State Council Decree No. 591 requires producers and importers of hazardous chemicals to complete registration with the National Registration Center for Chemicals before production or import. The implementing Measures for Registration of Hazardous Chemicals (Order No. 53) make registration a condition precedent for customs clearance of imported hazardous chemicals. For a buyer of concentrated acid or dilute acid solutions above the corrosivity threshold, the first relevant deadline is therefore the first commercial importation rather than a single statutory anniversary. A valid registration certificate corresponds to the specific product identity and CAS number; changes in concentration, use category, or supplier data require an update. Chinese safety data sheets must conform to GB/T 16483-2008 and use the GHS classification system of the GB 30000 series. In practice, a Chinese customs broker or contract importer may require the registration certificate before filing a customs declaration, and the absence of the certificate can delay release of a shipment.

Downstream storage and use in China engages additional permitting obligations: a hazardous chemical safety production license or safety use permit may be required depending on the quantity and site status. Sulfuric acid storage tanks, unloading stations, and transfer lines fall under safety facility design review and acceptance inspection under Decree No. 591. A buyer using sulfuric acid in a production process must confirm whether the site has an operating permit and whether the acid is within the facility’s approved inventory; a change in annual throughput can require a revised safety evaluation. These obligations are not superseded by the EU CLP date; they run in parallel and are verified separately.

At a concentration of 15% w/w sulfuric acid, the regulatory classification crosses a sharp boundary. The same solution at 14.9% by mass carries a label warning for skin irritation and serious eye irritation; at 15.0% the label flips to GHS05 corrosion, H314, and transport classification under UN 2796 or UN 1830 depending on concentration. This cliff-edge has direct consequences for packaging design. Absorbent containers, vented closures, and secondary containment specifications are less forgiving for a corrosive liquid; UN performance testing under ADR Chapter 6.1 and 49 CFR Part 178 require specific test designations. Sulfuric acid in both concentrated and diluted forms is Class 8, Packing Group II, so UN-tested packages are marked with the letter Y. A distribution center handling both 10% and 98% acid must not allow shared pump skids without a written changeover procedure; trace amounts of stronger acid in a diluted product can shift the delivered concentration and alter the label. Published data for this specific configuration is limited, but the 15% threshold is explicit in CLP Annex VI and is adopted by the GB 30000 series for skin corrosion/irritation.

When Sulfuric Acid Is Bought as a 98% Substance Rather Than an Aqueous Mixture

An entirely anhydrous or 98% sulfuric acid stream is a substance for CLP classification and, as such, would be subject to the earlier 1 May 2025 substance date for the 2023/707 hazard classes, not the 1 May 2026 mixture date. For buyers, this distinction changes which deadline controls. The same purchase order for 98% acid may list CAS 7664-93-9, while a diluted 37% stream may be a separate mixture with its own classification and poison centre obligations. The China regime does not split the deadline this way; both concentrated and dilute streams in the hazardous chemical catalogue are treated as hazardous chemicals and must be registered before first import if they meet the Chinese classification thresholds.

Material handling data for 98% H₂SO₄ establish density at 1.84 g/cm³ at 20 °C and solidification temperature at approximately 10 °C. The freezing point creates winter storage problems: unheated tank farms in northern China or northern EU may need tank heating or insulation to maintain temperature above 10 °C. A solidification event in a 98% acid line is operational rather than regulatory, but it can interrupt supply and alter sampling. For 93–98% acid, carbon steel storage is commonly used because the acid passivates the carbon steel surface; in dilute acid below 93%, the passivation behavior is lost and the corrosion rate increases sharply. Published material selection guidance such as NACE SP0294-2006 and manufacturer technical bulletins indicate that flow velocity, temperature, and acid concentration must be evaluated jointly; no single material is universally acceptable.

Compatibility boundaries are critical: concentrated sulfuric acid must not be mixed with water through a blind water addition line without a static mixer and thermal relief. The heat of dilution is sufficiently high to vaporize water violently if acid is added to water without agitation. Acid-to-water addition order is mandatory for safe operation. Carbon steel piping may tolerate 98% acid at low flow velocities, but the same material fails rapidly in 20% acid service. For dilute acid transfer, PTFE, PVDF, or resin-lined steel is specified. The EU 1 May 2026 deadline therefore arrives simultaneously with normal equipment inspection intervals. A buyer that replaces carbon steel piping with PVDF-lined steel to handle a new 20% acid product may need to update the engineering and safety data, but the EU CLP obligation is triggered by the product classification, not by the pipe material.

Sulfuric Acid Mist, Ventilation, and Exposure-Record Documentation

Occupational exposure limits create a separate data obligation for the purchaser’s site risk assessment. In the United States, 29 CFR 1910.1000 Table Z-1 retains a permissible exposure limit of 1 mg/m³ for sulfuric acid as an 8-hour time-weighted average. The American Conference of Governmental Industrial Hygienists publishes a threshold limit value of 0.2 mg/m³ for the thoracic particulate fraction, which is numerically lower and is used in many commercial hygiene plans. For a tank unloading station, an acid mist is formed when warm acid contacts humid air or when a vented tank cycles between fill and discharge. Enclosed sampling points, local exhaust, and continuous pH or conductivity alarms are standard engineering controls. The 2026 EU CLP revision does not alter these numeric limits, but the SDS Section 8 exposure controls must remain consistent with the updated compositional hazard data in Section 3. Where a 5% to 15% acid solution is classified only as an irritant, the exposure band may differ from the 98% corrosive stream, and the same fixed monitor located 2 m from the unloading manifold may require a different alarm set point. Published occupational exposure data for acid mist across the 15% threshold is limited; industrial hygienists typically default to the lower 0.2 mg/m³ value when concentration is variable.

Storage Turnover and Solidification at the 10 °C Freezing Point

Concentrated sulfuric acid at 98% has a freezing point near 10 °C and a density of 1.84 g/cm³ at 20 °C. A tank storing the acid outdoors in a northern rail spur without heat tracing may solidify during winter if the liquid temperature falls below the solidification point. Solidification does not violate the 1 May 2026 EU deadline, but it creates a physical contingency that complicates sampling for compliance verification. A block of frozen acid cannot be sampled for concentration; the sample drawn after thawing may show stratification that misrepresents the bulk composition. Storage tank heating elements are typically specified to maintain 25 °C to 35 °C, but localized overheating above 50 °C can accelerate corrosion of carbon steel at the heating coil surface. The resulting iron sulfate contamination may alter the appearance of the acid and, at trace levels, create an inaccurate reduced-sulfur odor. For China-bound acid, a distributor must verify that the heated storage configuration appears in the facility safety evaluation, because a change from unheated to heated storage can modify the process safety description.

Under the EU CLP 2023/707 amendment, a mixture placed on the market after 1 May 2026 must be classified, labelled, and packaged in accordance with the new hazard classes. If no new class applies, the label may remain unchanged; if a component triggers PMT or ED, the pictogram or signal word may change and the SDS Section 2.2 must list the new class. Some supply contracts treat a label-only change as a minor document update, but under CLP Article 31, a safety data sheet revision must be supplied without delay when new hazard information becomes available. The acid buyer must therefore require a revision date on the supplier SDS and compare it against the 1 May 2026 cutoff. A shipment landed on 2 May 2026 from a non-EU supplier using an old 2025 SDS may be nonconforming even if the product itself is unchanged.

Annual reporting obligations under Order No. 53 are attached to the registration certificate. The registered importer must report production, import quantities, and safety management data for the prior year. If the annual report has not been accepted, the registration may not be valid for the next import. This creates a rolling compliance deadline that is frequently missed when a buyer changes third-party distributor or port of entry. The EU 2026 date does not replace this annual Chinese filing; both must be current for a single shipment to enter without administrative delay.