When ammonium nitrate (NH₄NO₃) undergoes thermal decomposition, it produces nitrogen gas (N₂), oxygen gas (O₂) and water vapor (H₂O). The balanced chemical equation for this reaction is:

$$NH₄NO₃ → N₂ + O₂ + 2H₂O$$

According to this equation, for every mole of ammonium nitrate that reacts, one mole of nitrogen gas is produced.