An oxygen generator comprising - a composition for generating oxygen, the composition comprising an oxygen source, a peroxide decomposition catalyst, an ionic liquid and, if the ionic liquid is acidic, a basic compound, and - at least one tuner compact (20, 25, 30, 35, 40, 45) having a core shell structure comprising a core (22, 27, 33, 38, 42, 47) and one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46), wherein - a first shell layer (32, 37) completely surrounds the core (22, 27, 33, 38, 42, 47) and each further shell layer (21, 26, 31, 36, 41, 46) completely surrounds the underlying shell layer (21, 26, 31, 32, 36, 37, 41, 46), - at least one of the core (22, 27, 33, 38, 42, 47) and the one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46) consists of or comprises a compound selected from a peroxide decomposition catalyst, an acidic compound or a basic compound, with mixtures comprising both an acidic compound and a basic compound or comprising both an acidic compound and a peroxide decomposition catalyst within the core (22, 27, 33, 38, 42, 47) or within the same shell layer (21, 26, 31, 32, 36, 37, 41, 46) being excluded, and - the core (22, 27, 33, 38, 42, 47) and the one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46) are capable of decomposing or dissolving or disintegrating upon contact with the composition for generating oxygen, and further wherein - the oxygen source comprises a peroxide compound, - the ionic liquid is in the liquid state at least in the temperature range from -10°C to +50°C, and - the peroxide decomposition catalyst is a metal oxide compound and/or a metal salt, wherein the metal oxide compound is an oxide of a single metal or of two or more different metals, said metal(s) being selected from the metals of groups 2 to 14 of the periodic table of the elements, and wherein the metal salt comprises one single metal or two or more different metals, and an organic and/or an inorganic anion. - a composition for generating oxygen, the composition comprising an oxygen source, a peroxide decomposition catalyst, an ionic liquid and, if the ionic liquid is acidic, a basic compound, and - at least one tuner compact (20, 25, 30, 35, 40, 45) having a core shell structure comprising a core (22, 27, 33, 38, 42, 47) and one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46), wherein - a first shell layer (32, 37) completely surrounds the core (22, 27, 33, 38, 42, 47) and each further shell layer (21, 26, 31, 36, 41, 46) completely surrounds the underlying shell layer (21, 26, 31, 32, 36, 37, 41, 46), - at least one of the core (22, 27, 33, 38, 42, 47) and the one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46) consists of or comprises a compound selected from a peroxide decomposition catalyst, an acidic compound or a basic compound, with mixtures comprising both an acidic compound and a basic compound or comprising both an acidic compound and a peroxide decomposition catalyst within the core (22, 27, 33, 38, 42, 47) or within the same shell layer (21, 26, 31, 32, 36, 37, 41, 46) being excluded, and - the core (22, 27, 33, 38, 42, 47) and the one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46) are capable of decomposing or dissolving or disintegrating upon contact with the composition for generating oxygen, and further wherein - a first shell layer (32, 37) completely surrounds the core (22, 27, 33, 38, 42, 47) and each further shell layer (21, 26, 31, 36, 41, 46) completely surrounds the underlying shell layer (21, 26, 31, 32, 36, 37, 41, 46), - at least one of the core (22, 27, 33, 38, 42, 47) and the one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46) consists of or comprises a compound selected from a peroxide decomposition catalyst, an acidic compound or a basic compound, with mixtures comprising both an acidic compound and a basic compound or comprising both an acidic compound and a peroxide decomposition catalyst within the core (22, 27, 33, 38, 42, 47) or within the same shell layer (21, 26, 31, 32, 36, 37, 41, 46) being excluded, and - the core (22, 27, 33, 38, 42, 47) and the one or more shell layers (21, 26, 31, 32, 36, 37, 41, 46) are capable of decomposing or dissolving or disintegrating upon contact with the composition for generating oxygen, and further wherein - the oxygen source comprises a peroxide compound, - the ionic liquid is in the liquid state at least in the temperature range from -10°C to +50°C, and - the peroxide decomposition catalyst is a metal oxide compound and/or a metal salt, wherein the metal oxide compound is an oxide of a single metal or of two or more different metals, said metal(s) being selected from the metals of groups 2 to 14 of the periodic table of the elements, and wherein the metal salt comprises one single metal or two or more different metals, and an organic and/or an inorganic anion.