INCIDENT TITLE: Mixing of acid and oxidiser

During the refilling of the reactants into the tanks on the truck, sodium nitrite was added by mistake into the tank of acetic acid. The hose connections are non-drip quick couplings, purposely of different sizes in order to make this type of mistake impossible. But they were partially worn out and the operator managed to make the wrong connection without noticing. Some NOx fumes came immediately out of the acid tank.