There is no Class 3 Division 2; Class three has no subdivisions.
Class 4 Division 2, more often called Division 4.2, is for spontaneously combustible materials
DOT Class 2, Division 1 (more properly called Division 2.1) is for flammable gases.
Class 6, Division 2 (more properly called Division 6.2) is for infectious agents.
DOT Class 2, Division 1 (more properly called Division 2.1) is for flammable gases.
Class 4 Division 2, more often called Division 4.2, is for spontaneously combustible materials
liquefied gas
Division 4.2 is spontaneously combustible material.
Class 2 division 1, more properly called division 2.1, is for flammable gasses.
"Non-flammable compressed gas" is the formal terminology. This class/division includes carbon dioxide (co2) cylinders, air tanks, and many industrial gasses described as "inert". Flammable gasses/aerosols, and toxic gasses/aerosols are also in class 2, but different divisions (2.1, and 2.3 respectively)
Class 4 division 1 (more properly called Division 4.1) is for flammable solids.
World Class