Even when the general segregation table might otherwise permit a lesser separation, what special absolute rule applies to Class 8 (corrosive) liquids in relation to Class 4 (flammable solid) or Class 5 (oxidizing) materials under 49 CFR 177.848?

49 CFR 177.848(e)(3)

A corrosive leak that drips down onto a flammable solid or an oxidizing material below it can start a fire or accelerate one well beyond what either material would cause on its own. This rule exists specifically to prevent that vertical or adjacent exposure, which is a different hazard pathway than the horizontal distance rules most loaders are used to thinking about.