Official microsoft documentation for hazardous material management explicitly states how to handle the 4 hazmat classes that don't have divisions. Haz classes 3, 7, 8 and 9 have no further division / subclass to them. Documentation says:

For classes that don't have any divisions, create a division where the code is 0. For example, in the IATA regulation, class-7 radioactive materials have no subdivisions. In this case, you will create a 0 division that you can associate with a released product when you assign the class."

If you do this, and create a HazMat division of "0" for class 3 and then again for class 7, you will get an error about uniqueness on the table. Alternatively, creating a single hazmat division record of "0" and hoping it can be used across multiple hazmat classes is also a bust. The class field dictates the automatic filtering of the field.

The easy solution of course is to change the system to match the released documentation so we can use multiple divisions of "0".

The BETTER solution would be to make HAZMAT division not mandatory because tons of regulated products do not have a division within their class and it was a foolish assumption to make in the system.