Ammo Nitrate needs a catalyst in order to explode.  Not true, https://chemistry.stackexchange.com/questions/138440/how-does-ammonium-nitrate-explode-on-its-ownHowever, it is a strong oxidizing agent that can detonate under certain conditions such as temperature, fire, confinement, and presence of impurities (e.g., KCl), which can be act as a promoter to detonate (Ref.2).