The Hazmat Segregation Table, Explained
Updated October 27, 2026
Some hazardous materials react dangerously if they mix, so the rules say which classes may not ride in the same vehicle. The segregation table in 49 CFR 177.848 sets those limits, and the CDL hazmat test usually asks a question or two about it. Here is how to read it, the combinations worth remembering, and the extra loading rules for explosives and radioactive materials.
How to read the table
Find one material’s class or division down the side and the other’s across the top. The box where they meet tells you the rule:
| Symbol | Meaning |
|---|---|
| Blank | No restriction |
| X | May not be loaded, transported or stored together in the same vehicle |
| O | May not be loaded together unless separated so that, if packages leaked, the materials could not mix |
| * | Both are Class 1 explosives; use the separate compatibility table for explosives |
| A | Ammonium nitrate (UN1942) and ammonium nitrate fertilizer may ride with Division 1.1 or 1.5 despite the X |
The table applies to packages that must be labeled or placarded. If a package has a subsidiary hazard label, you also apply the segregation for that subsidiary hazard when it is stricter.
Combinations to remember
| Materials | Rule |
|---|---|
| Division 1.1 or 1.2, or Division 1.5, with any other hazard class | X (except ammonium nitrate under note A) |
| Class 7 radioactive with Division 1.1, 1.2 or 1.5 | X |
| Class 7 radioactive with Division 2.1 flammable gas | O |
| Division 2.3 poison gas, Hazard Zone A, with Class 3, 4, 5 or 8 liquids | X |
| Division 2.3 poison gas, Hazard Zone B, with Class 3, 4, 5 or 8 liquids | O |
| Division 2.1 flammable gas with 2.3 Hazard Zone A | X |
| Class 3 flammable liquid with Division 5.1 oxidizer | O |
| Division 4.2 with Class 8 liquids | X |
| Division 4.1 or 4.3 with Class 8 liquids | O |
| Division 6.1 Packing Group I, Hazard Zone A, with Class 3, Class 8 liquids or Divisions 4.1, 4.2, 4.3, 5.1, 5.2 | X |
| Division 2.2 non-flammable gas with anything except Division 1.1, 1.2 or 1.5 | No restriction |
| Class 3 with Class 8 liquids | No restriction |
Two more rules sit outside the grid:
- Cyanides and acids may not be loaded together if mixing would produce hydrogen cyanide gas.
- Class 8 corrosive liquids may never be loaded above or next to Class 4 or Class 5 materials, even when separated.
Class 1 explosives loading rules
- Turn the engine off before loading or unloading.
- Disable any cargo heater by draining or removing its fuel tank and disconnecting its power source.
- Check the cargo space for bolts, screws, nails or broken boards that could damage packages.
- For Division 1.1, 1.2 or 1.3, the floor must be tight and lined with a non-metallic material or a non-ferrous metal.
- Never use hooks or other metal tools, and never drop, throw or roll the packages.
- Do not take damaged packages, or any that show dampness or an oily stain.
- Do not carry Division 1.1 or 1.2 in a combination with a marked or placarded cargo tank, or with more than two cargo-carrying vehicles.
Class 7 radioactive materials and the Transport Index
Packages labeled RADIOACTIVE YELLOW-II or YELLOW-III carry a number called the Transport Index (TI), printed on the label by the shipper. It tells how much control the package needs in transport.
- Add the TI numbers of all packages on the vehicle. The total may not exceed 50 (except for exclusive use shipments).
- How close the packages may be to people, animals and undeveloped film depends on that total. The higher the total TI, the farther away they must be, using the table in 49 CFR 177.842.
- Block and brace the packages so they cannot shift, and do not stay in the vehicle longer than necessary.
- Packages with the YELLOW-III label require RADIOACTIVE placards in any amount.
Test yourself
-
In the segregation table, what does an X where two classes meet mean?Answer: AAn X means the materials may not be loaded, transported or stored together in the same transport vehicle. An O allows them together only if separated so leaks could not mix.
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The box where two classes meet in the segregation table is blank. What does that tell you?Answer: BA blank space, or a class that is not in the table, means no segregation restriction applies. The packages must still be secured against shifting.
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You have packages of Class 7 radioactive material. May you also load Division 1.1 explosives in the same vehicle?Answer: CThe segregation table shows an X for Class 7 with Divisions 1.1 and 1.2, so they may not be loaded together at all.
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You must haul a Class 3 flammable liquid and a Division 5.1 oxidizer. What does the segregation table require?Answer: DThe table shows an O for Class 3 with Division 5.1. They may be loaded together only if separated so the materials would not mix if packages leaked.
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The segregation table shows an asterisk (*) where two explosives divisions meet. What do you do?Answer: AThe asterisk means segregation between different Class 1 materials is governed by the compatibility table for explosives in 49 CFR 177.848(f), not the main segregation table.
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What is the Transport Index on a radioactive package?Answer: BThe shipper prints the Transport Index on RADIOACTIVE YELLOW-II and YELLOW-III labels. It shows the degree of control needed, which limits how many packages ride together and how close they may be to people.
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Your vehicle carries radioactive packages with transport indexes of 12, 15 and 20. A shipper offers one more with a TI of 4. May you take it (not an exclusive use shipment)?Answer: CThe total transport index in one vehicle may not exceed 50. The packages aboard add up to 47, and adding a TI of 4 would make 51.
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Your trailer holds Division 1.5 blasting agents. May you add cylinders of a Division 2.2 non-flammable gas?Answer: DDivision 2.2 is unrestricted with most classes, but the table shows an X for Division 2.2 with Divisions 1.1, 1.2 and 1.5, so they may not be loaded together.
See also: hazard classes and hazmat placards.
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