Hazmat Segregation Table PDF: Reading the Grid and Footnotes

The hazmat segregation table is a grid inside 49 CFR 177.848(d) that tells you whether two hazardous materials can travel in the same truck. You find the hazard class or division of each material, locate the cell where they intersect, and read the symbol: “X” means they cannot ride together, “O” means they can ride together only if separated so leaking contents cannot mix, and a blank cell means no segregation restriction applies. The mechanics are simple once you know where to look and which rules sit outside the grid itself.

Where the Official Table Lives

There is no standalone government PDF of the segregation table, which is why the search turns up so much noise. The authoritative version is in 49 CFR 177.848(d), viewable at the electronic Code of Federal Regulations (eCFR.gov) or the Cornell Law mirror.¹ PHMSA publishes DOT Chart 17, a printable reference on markings, labeling, and placarding that includes a condensed segregation chart.² Chart 17 works as a visor card, but it omits exceptions, subsidiary-hazard rules, and absolute prohibitions. For any real compliance decision, use the regulation.

What to Look Up Before You Touch the Grid

You need two facts about every material in the load: its hazard class or division, and, where it applies, its packing group. Both come from the Hazardous Materials Table at 49 CFR 172.101. Column 3 gives the class or division; Column 5 gives the packing group.³ Packing Group I is the greatest danger, II is medium, and III is the least. Class 2 gases, Class 7 radioactives, and Division 6.2 infectious substances have no packing group.

Knowing only the broad class is not enough. The segregation grid splits Class 1 explosives into six divisions and separates Class 2 into flammable gas (2.1), non-flammable/non-toxic gas (2.2), and poison gas Zone A and Zone B (2.3). Division 6.1 is further sorted by packing group and hazard zone in certain rows. Look up the exact division before you go to the grid.

Reading the Grid

The table is a matrix with hazard class divisions running down the rows and across the columns. Pick one material’s row and the other’s column, and read the cell where they meet.¹

X — the materials may not be loaded, transported, or stored together in the same vehicle or storage facility during transport.
O — the materials may not be loaded together unless separated in a way that would keep their contents from mixing if both packages leaked under normal transport conditions.
Blank — no segregation restriction applies from the table.
Asterisk (*) — appears where two Class 1 explosive subdivisions intersect. Explosives segregate from each other by compatibility group letter, and the asterisk sends you to a separate compatibility-group table.

A Worked Example

You want to ship a flammable gas (Class 2.1) with an oxidizer (Class 5.1). Cross 2.1 and 5.1 on the grid and the cell reads “O.” The two can share the vehicle only if they are physically separated well enough that a leak from either package could not reach the other. Now try Division 1.1 explosives against 5.1 oxidizers. That cell is “X.” They cannot share the truck at all.

Subsidiary Hazard Labels Can Change the Answer

A single package can carry a primary hazard class and one or more subsidiary hazard labels, and the regulation requires you to check the grid against every label on both packages. Whichever result is most restrictive controls.⁴ A Class 3 flammable liquid with a subsidiary Class 8 corrosive label is treated as both. If the Class 3 comparison against another material produces a blank cell but the Class 8 comparison produces an “O,” the “O” wins.

One narrow exception: materials of the same hazard class can share space without regard to subsidiary-hazard segregation, as long as they cannot react dangerously with each other to produce fire, flammable or toxic gases, or corrosive or unstable byproducts.

Footnotes and Prohibitions That Override the Grid

Some rows carry a note “A” in the second column. This covers ammonium nitrate (UN1942) and ammonium nitrate fertilizer, which may be loaded with Division 1.1 or 1.5 explosives despite the “X” that would otherwise apply, unless separately prohibited by 49 CFR 177.835(c).⁴ Most shippers will never use this carve-out, but it is the kind of footnote you miss if you read only the grid.

Paragraph (c) of 177.848 flatly prohibits three combinations regardless of what the grid shows:

Cyanides, cyanide mixtures, or cyanide solutions with acids, if the combination could generate hydrogen cyanide gas.
Division 4.2 spontaneously combustible materials with Class 8 liquids.
Division 6.1 Packing Group I Hazard Zone A materials with Class 3, Class 8 liquids, or any material in Division 4.1, 4.2, 4.3, 5.1, or 5.2.

No amount of separation within the same vehicle is considered adequate for these combinations.¹

What “O” Separation Actually Requires

When the grid shows “O,” you need physical separation sufficient to prevent commingling if packages leak. Common approaches are a solid barrier between the incompatible packages, intervening open space, or non-hazardous freight loaded between them. The practical test is simple: if both packages leaked under the vibration and shifting of normal transport, would the contents reach each other? If yes, the separation is not enough.

A positioning rule sits on top of that requirement. Class 8 corrosive liquids may never be loaded above or adjacent to Class 4 or Class 5 materials.¹ A corrosive dripping onto a flammable solid or oxidizer is a known reaction path. The one exception is a truckload shipment where the shipper knows the specific contents cannot cause a fire or dangerous release of heat or gas.

Same-Class Materials Can Still Be Incompatible

A blank cell is not a guarantee of safety. Two materials in the same class can still react dangerously with each other. Two Division 5.1 oxidizers meet at a blank cell, but if combining them would produce fire, toxic gas, or unstable compounds, they must be segregated anyway. The regulation puts the burden on the shipper to know whether same-class materials are compatible beyond what the table displays.

The Table Is for Highway Transport Only

49 CFR 177.848 governs motor vehicle transport. When a truck carrying hazmat is loaded onto a vessel other than a ferry, segregation shifts to 49 CFR 176.83(b), which uses a different and often more detailed framework.¹ Air and rail have their own rules under separate parts of Title 49. On multimodal shipments, do not assume the highway table covers every leg.

Penalties for Getting It Wrong

Segregation is among the more heavily penalized hazmat violations. A person who knowingly violates federal hazmat transportation requirements faces a civil penalty of up to $102,348 per violation. If the violation results in death, serious injury, or substantial destruction of property, the maximum rises to $238,809. Each day a continuing violation persists counts as a separate offense. Training violations carry a minimum penalty of $617.⁵ The cost of a misread cell compounds fast.

1
eCFR. 49 CFR 177.848 – Segregation of Hazardous Materials
2
Pipeline and Hazardous Materials Safety Administration. Hazardous Materials Markings, Labeling and Placarding Guide
3
eCFR. 49 CFR 172.101 – Purpose and Use of Hazardous Materials Table
4
GovInfo. 49 CFR 177.848 – Segregation of Hazardous Materials
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Federal Register. Revisions to Civil Penalty Amounts, 2025