In recent years, the use of nitrogenous industrial explosives has come under intense scrutiny by environmental agencies due to emission of toxic fumes to the atmosphere during blasting of ammonium nitrate based explosives. Ammonium nitrate (AN) is a major ingredient in ammonium nitrate fuel oil (ANFO), and emulsion explosives, which are commonly applied in trench or surface mines blasting, and construction operations. It is well known that ammonium nitrate based explosives release toxic fumes (which contains NO and NO2 emissions) under certain blasting condition, and/or oxygen rich explosive formulations. We investigated the effect of potassium on crystal structure, and thermal behaviour of ammonium nitrate. We observed multiphase structures in co-recrystallised ammonium nitrate containing low (2-4 mol %) and high (>25 mol %) concentrations of potassium in the crystallisation solution; mol % is based only on K+ and NH4
+. Co-recrystallised salts were characterise using X-ray diffraction (XRD), Scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS), Inductively coupled plasma - optical emission spectroscopy (ICP-OES), and Thermogravimetric analyser and differential scanning calorimeter (TGA/DSC). In addition, we report concentration profiles of NO during thermal analyses of corecrystallised potassium ammonium nitrates. The results obtained from thermal decomposition of the co-recrystallised potassium ammonium nitrate salts showed decrease in production of NO. and 3-5 mol % K was the optimal concentration when compared with pure AN.