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 having a core shell structure comprising a core and one or more shell layers , wherein - a first shell layer completely surrounds the core and each further shell layer completely surrounds the underlying shell layer , - at least one of the core and the one or more shell layers 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 or within the same shell layer being excluded, and - the core and the one or more shell layers 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 having a core shell structure comprising a core and one or more shell layers , wherein - a first shell layer completely surrounds the core and each further shell layer completely surrounds the underlying shell layer , - at least one of the core and the one or more shell layers 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 or within the same shell layer being excluded, and - the core and the one or more shell layers are capable of decomposing or dissolving or disintegrating upon contact with the composition for generating oxygen, and further wherein - a first shell layer completely surrounds the core and each further shell layer completely surrounds the underlying shell layer , - at least one of the core and the one or more shell layers 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 or within the same shell layer being excluded, and - the core and the one or more shell layers 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. <EOS>