NOVELTY - Materials generating ammonia irreversibly are safely used by bringing a first ammonia generating material (1a) capable of generating ammonia irreversibly and/or its decomposition product and a second ammonia storage material (2a)capable of reversibly or irreversibly adsorbing or absorbing ammonia and/or its decomposition product into fluid communication with each other, when a vapor pressure of the first material and/or its decomposition product is at or higher than a pressure threshold, for adsorbing or absorbing ammonia released from the decomposition of the first material.    USE - The method is for safe use of materials generating ammonia irreversibly (claimed). The materials can be used as solid or liquid storage media for ammonia.    ADVANTAGE - The method greatly increases the safety when using the materials generating ammonia irreversibly and/or having relatively high ammonia vapor partial pressures (e.g., ammonia dissolved in water); and achieves a high degree of safety.    DETAILED DESCRIPTION - Safe use of materials generating ammonia irreversibly includes bringing a first ammonia generating material (1a) capable of generating ammonia irreversibly and/or its decomposition product and a second ammonia storage material (2a) capable of reversibly or irreversibly adsorbing or absorbing ammonia and/or its decomposition product into fluid communication with each other, when a vapor pressure of the first ammonia generating material and/or its decomposition product is at or higher than a pressure threshold, for adsorbing or absorbing ammonia released from the decomposition of the first ammonia generating material. The second ammonia storage material has a lower ammonia vapor pressure than the first ammonia generating material, and is only partially saturated with or completely void of ammonia. INDEPENDENT CLAIMS are included for:    (1) an apparatus (100) for storing and delivering ammonia, comprising first and second storing/delivery units (1, 2) connectable in fluid communication and containing the first ammonia generating material and the second ammonia storage materials, where the second material in the second unit has a lower vapor pressure than the first material and/or its decomposition product when being at a pressure threshold suitable for adsorbing or absorbing ammonia from the first material and/or its decomposition product; and    (2) an automotive nitrogen oxides (NO x) treatment system, comprising the apparatus for storing and delivering ammonia.    The first and second storing/delivery units each comprise a heater (3a, 3b). The first storing/delivery unit has a first shell (4a). The second storing delivery unit has a second shell (4b). The apparatus also includes a control valve arrangement (6) for connecting at least the first storing/delivery unit with an ammonia consumer or the device for decomposing the ammonia generating material, where the ammonia consumer is a catalyst for selective catalytic reduction (SCR) of NO x in oxygen-containing exhaust gas, a catalytic device for splitting ammonia into nitrogen and oxygen, or a fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic view of the ammonia storage and delivery apparatus.    First and second storing/delivery units (1, 2)    First ammonia generating material (1a)    Second ammonia storage material (2a)    Heater (3a, 3b)    First shell (4a)    Second shell (4b)    Ammonia storage and delivery apparatus (100)