What Is Hazmat? Dangerous Goods in Transport

What Does Hazmat Mean?

Hazmat is short for hazardous materials: substances or articles that, because of their chemical, physical or biological properties, pose a risk to health, safety or the environment while being handled, stored or transported — fuels, compressed gases, corrosives, explosives, toxic or radioactive substances, among others.

The term is used across the logistics chain: "hazmat cargo", "hazmat transport" or "hazmat certification" distinguish these operations from general freight, because they carry extra rules, paperwork and training requirements. Whether a shipment counts as hazmat doesn't depend on the quantity moved or the size of the company: it depends on the nature of the substance, so a small business hauling a few drums of solvent is bound by the same underlying rules as a full tanker truck of fuel.

The 9 Hazard Classes

The UN classification — adopted by Mexican regulation and most of the world — divides dangerous goods into 9 classes:

1. Explosives (fireworks, ammunition)
2. Gases (LP gas, oxygen, aerosols)
3. Flammable liquids (gasoline, solvents, alcohols)
4. Flammable solids (sulfur, phosphorus)
5. Oxidizers and organic peroxides
6. Toxic and infectious substances (pesticides, biological waste)
7. Radioactive material
8. Corrosives (acids, caustic soda)
9. Miscellaneous (lithium batteries, dry ice)

Each substance also has a four-digit UN number (for example, UN 1203 = gasoline) that identifies it on documents, packaging and placards. Several classes also carry a packing group (I, II or III) that indicates how severe the hazard is: group I marks the highest danger, group III the lowest. Gasoline, for instance, falls under class 3 with packing group II, because its flash point is low but not extreme. That combination — class, UN number and packing group — is exactly what later gets translated, field by field, into the CFDI with Carta Porte.

How to Tell If Your Cargo Is Hazmat

Before arranging transport, there's one concrete question to answer: does my cargo fall into one of the 9 classes? Three sources settle most cases:

• The safety data sheet (SDS) the manufacturer or supplier must provide: it lists the hazard class, the UN number and handling conditions.
• The product's technical sheet, which usually states whether the packaging needs hazard pictograms.
• The SAT's product and service catalog (c_ClaveProdServCP), which already flags each code with a hazard indicator: "0" if the product isn't dangerous, "1" if it is, and "0,1" when it depends on the presentation being invoiced.

If any of those sources flags the cargo as dangerous, the operation has to be treated as hazmat from the freight quote all the way through stamping the CFDI.

What Hazmat Transport Requires in Mexico

In Mexico, road transport of hazardous materials and waste is governed by the federal dangerous-goods transport regulation and by SICT standards, including NOM-002-SCT (which lists the most commonly transported hazardous substances and materials) and NOM-004-SCT (which defines the placarding system the unit must carry). In practice, a hazmat operation requires elements worth splitting into two fronts.

Documentation and placarding on the unit

• Placarding according to the hazard class, visible from a distance on the unit
• Shipping documentation with UN number, class, quantity and packaging type
• An authorized route, since not every road allows dangerous cargo
• An emergency response plan for a spill, leak or accident

Permits and training for the carrier

• A specific SICT permit for both the carrier and the vehicle
• Drivers with a federal type E license and certified dangerous-goods training
• Insurance covering third-party and environmental damage, on top of general cargo coverage

Missing any of these isn't just an administrative violation: in an accident, it can void the insurance coverage and get the unit pulled off the road until it's resolved.

Worked Example: Declaring a Gasoline Shipment in the Carta Porte

Here's how the flow looks when a company moves gasoline (UN 1203) between two plants:

1. Identification: the logistics team confirms in the safety data sheet that the substance is UN 1203, class 3, packing group II.
2. Quote and route: a certified class-3 unit is booked, with an authorized route and a type E licensed driver.
3. Loading and placarding: the unit is placarded with the class 3 diamond and the number 1203 visible.
4. Invoicing: the CFDI with Carta Porte declares the hazardous-material key for UN 1203 (c_MaterialPeligroso catalog) and the packaging type (c_TipoEmbalaje catalog); if the key is generic, it adds the specific chemical name in parentheses, as NOM-002-SCT requires.
5. Stamping: the PAC validates the keys against the official catalogs before stamping; if any key doesn't match, the CFDI is rejected before it goes out.

The same flow applies, with its own UN number, to any other substance across the 9 classes.

Hazmat and the Carta Porte: Where They Meet

Since Mexico's SAT made the Carta Porte complement mandatory, hazmat data no longer lives only on paper: if you move dangerous goods, the complement requires declaring the UN number, the hazardous-material key (c_MaterialPeligroso catalog) and the packaging type (c_TipoEmbalaje) for every item. If the key chosen corresponds to a generic substance — "organic liquid compound", for example — the complement also asks for the specific chemical name in parentheses. An error in any of those fields makes the CFDI technically invalid even if it was stamped, because the PAC and the SAT cross-check the keys against the official catalogs.

That is why companies moving hazmat cargo tend to automate the complement: the system pulls trip data and validates the keys against the official catalogs before stamping, instead of hand-typing them trip by trip, which is where most keying errors pile up.

Common Mistakes When Transporting or Invoicing Hazmat Cargo

These are the mistakes that generate the most rejections and fines in real operations:

• Using a generic hazard key when a specific one exists for the substance, instead of the exact chemical name.
• Skipping the packaging type or entering one that doesn't match the actual container.
• Placarding the unit with the wrong diamond for the substance's real class.
• Dispatching without checking that the SICT permit or the driver's type E license is still valid.
• Typing the UN number by hand on every trip, which multiplies the risk of keying errors against a system-validated catalog.

None of these mistakes are exclusive to large companies: they show up just as often in small fleets that still fill out the Carta Porte field by field.

Hazmat in the Logistics Chain: From 1PL to 5PL and the Role of Automation

Not every company moves its own hazmat cargo: many outsource it to logistics operators, and the level of outsourcing — from 1PL to 5PL — determines who is responsible for certification, placarding and correctly filling out the Carta Porte. When transport is outsourced to a 3PL or 4PL, the company that owns the cargo is still responsible for correctly declaring the hazardous material on its own CFDI, even though the unit and the driver belong to a third party.

So beyond who operates the unit, the part that benefits most from automation is the paperwork: having the UN number, the hazard key and the packaging type pulled from the product's catalog instead of typed by hand on every trip. It's the same principle behind workflow automation in any repetitive process: less manual entry, fewer CFDIs rejected over a mistyped field.

Frequently Asked Questions

Are hazmat and dangerous goods the same thing?

Yes. Hazmat is simply the English term (hazardous materials) used in industry and international logistics; Mexican regulation refers to "materiales y residuos peligrosos", but both cover the same 9 classes and the same UN numbers.

What happens if I declare the hazardous material wrong in the Carta Porte?

The CFDI can end up technically invalid even if the PAC stamped it, because the key doesn't match the official catalog. That can lead to the document being rejected in a SAT review and, on the road, to the unit being unable to account for the cargo it's carrying.

Does every company moving a dangerous substance need an SICT permit?

Yes, if the transport happens by federal road on general communication routes. The permit applies to the carrier and the vehicle, regardless of whether the cargo belongs to the company or to a client.

How do I know which hazard key to use when invoicing?

It comes from the SAT's c_MaterialPeligroso catalog, tied to the substance's UN number. If the key is generic, the specific chemical name has to be added in parentheses.

Is gasoline always declared the same way in the Carta Porte?

The UN number (1203) and the class (3) don't change, but the packaging type depends on how it's transported: a bulk tanker isn't the same as sealed drums, so that field gets checked on every trip.

Does your operation move dangerous goods and need error-free Carta Porte stamping? At AISDC we integrate CFDI 4.0 invoicing with the Carta Porte complement directly into your transport system, with automatic key validation for manufacturing and other sectors that move hazmat cargo. Get in touch.