Calcium Carbide Reacts With Water and Releases Acetylene — Don't Book It as General Cargo

Overview

Calcium carbide — you may know it as CaC₂ — is a Chinese export under HS 2849.10 (customs code 2849100000), CAS 75-20-7. On the water it travels as UN 1402, Class 4.3: "substances that emit flammable gas when wet." Packing group II.

Put simply: the only thing that decides its class is the dangerous-goods classification report from an accredited lab — not your gut, not last year's shipment, and not what the factory sales rep told you on WeChat. Class 4.3 means one drop of water starts a reaction that throws off acetylene and a lot of heat. And acetylene, as you know, goes up the second it meets a spark.

Here's the thing: you can't put out a calcium carbide fire with water. Sand, CO₂, or dry soda ash. Forget that in a panic and you'll grab the hose, which is the worst move you can make.

Why is 4.3 harder than the other classes? You can't ship it as general cargo, and you can't hide behind the limited-quantity exemption either — LQ goods are still dangerous goods, and the filing duty is just as real. Plenty of shippers think "small volume, no problem." That's exactly where they sink.

Key Details

Calcium carbide exports must go through the DG booking channel, and the original dangerous-goods packing certificate is the hard gate (no certificate, no container out the door). Packaging is limited to sealed metal drums (UN 1A1) with desiccant inside.

It's also a supervised product, so the factory files for inspection first. Your MSDS needs all 16 sections in Chinese and English with an emergency phone number, and the maritime declaration goes in 24 to 48 hours before sailing. Miss one link and it comes back.

Carriers are picky about 4.3, and you must not pick up or stuff the container until the DG approval receipt is in hand — that single rule has stopped more than a few impatient shippers. Frankly, rushing it is how drums end up sitting on the quay in August heat.

Looking Ahead

Misdeclaring as general cargo at worst costs you a back-charge and a fine.

Let the drums take on moisture and it's a different story — acetylene builds inside the box and the whole container becomes a bomb. This isn't about money. It's about whether you end up in the hospital. Why bet your life to save a few days?

Implications

Step one: start 4 to 6 weeks before departure, run the hazardous-characteristics classification test first, lock in UN 1402 / Class 4.3 / PG II, then make the four core parameters — UN number, shipping name, hazard class, packing group — identical across your MSDS, classification report, DG packing cert, booking note, maritime declaration, customs declaration and bill of lading, because one wrong character gets the box rejected at the gate.

Step two: get the paperwork together — performance certificate plus use-appraisal gives you the original packing cert, the factory inspection, the 16-section MSDS, and the DG application form. Do it early; don't wait for booking day.

Step three: watch the packaging and storage like a hawk. Sealed metal drum plus desiccant, UN mark clean and in date; photograph the stuffing, keep the whole voyage moisture-proof, and don't let rain soak it before arrival.

The catch is this: the class is set by the accredited lab, and what I've described is the general flow — your specific product follows your own test report. My read: carriers will tighten 4.3 moisture checks through the August humidity window, so the certificate you file in July is already soft by September.

Follow these three steps and your calcium carbide sails clean. Ship it in a bare drum to save time and, in August's humidity, you're gambling with your own safety. Your next move: send us your product name and we'll confirm the class before you book.