Ammonium nitrate is an oxidizing agent, so can't touch the potassium nitrate susceptible to thermal decomposition temperature, decomposition products, are also different.
Also is not burning, because he does not need oxygen to combustion, thermal decomposition is accurate.
At 110 ° C: NH4NO3 → NH3+HNO3 at 185 ~ 200 ° C: NH4NO3 → N2O+2H2O at or above 230 ° C, while the weak light: 2NH4NO3 → 2N2+O2+4H2O at or above 400 ° C, explosion: 4NH4NO3 → 3N2+2NO2+8H2O above the nitrogen dioxide, ammonia gas, on the respiratory tract has a strong irritant, toxic