High Quality Content by WIKIPEDIA articles! ANFO (or AN/FO, for ammonium nitrate/fuel oil) is a widely used bulk industrial explosive mixture. It consists of 94 percent porous prilled ammonium nitrate (NH4NO3), (AN) that acts as the oxidizing agent and absorbent for the fuel — six percent Number 2 Fuel Oil (FO). Strictly speaking, compositions that do not meet the 94%AN/6%FO formulation are not ANFOs.