An aircraft fuel cell system, comprising a high pressure hydrogen concentration zone housing equipment having a high operating pressure; a low pressure hydrogen concentration zone housing equipment having a lower operating pressure, the low pressure hydrogen concentration zone being different and separate from the high pressure hydrogen concentration zone , each zone being provided as a separate volume with physical boundaries delineating the zone area; wherein the high pressure hydrogen concentration zone comprises a hydrogen concentration sensor , and the low pressure hydrogen concentration zone comprises a hydrogen concentration sensor ; and a blower system configured to provide dilution air to the low pressure hydrogen concentration zone based on hydrogen concentration detected by the hydrogen concentration sensor of the low pressure hydrogen concentration zone and thereby provide continuous dilution of hydrogen-containing gas in the low pressure hydrogen concentration zone ; and provide dilution air to the high pressure hydrogen concentration zone based on hydrogen concentration detected by the hydrogen concentration sensor of the high pressure hydrogen concentration zone and thereby provide continuous dilution of hydrogen-containing gas in the high pressure hydrogen concentration zone , . a high pressure hydrogen concentration zone housing equipment having a high operating pressure; a low pressure hydrogen concentration zone housing equipment having a lower operating pressure, the low pressure hydrogen concentration zone being different and separate from the high pressure hydrogen concentration zone , each zone being provided as a separate volume with physical boundaries delineating the zone area; wherein the high pressure hydrogen concentration zone comprises a hydrogen concentration sensor , and the low pressure hydrogen concentration zone comprises a hydrogen concentration sensor ; and a blower system configured to provide dilution air to the low pressure hydrogen concentration zone based on hydrogen concentration detected by the hydrogen concentration sensor of the low pressure hydrogen concentration zone and thereby provide continuous dilution of hydrogen-containing gas in the low pressure hydrogen concentration zone ; and provide dilution air to the high pressure hydrogen concentration zone based on hydrogen concentration detected by the hydrogen concentration sensor of the high pressure hydrogen concentration zone and thereby provide continuous dilution of hydrogen-containing gas in the high pressure hydrogen concentration zone , . provide dilution air to the low pressure hydrogen concentration zone based on hydrogen concentration detected by the hydrogen concentration sensor of the low pressure hydrogen concentration zone and thereby provide continuous dilution of hydrogen-containing gas in the low pressure hydrogen concentration zone ; and provide dilution air to the high pressure hydrogen concentration zone based on hydrogen concentration detected by the hydrogen concentration sensor of the high pressure hydrogen concentration zone and thereby provide continuous dilution of hydrogen-containing gas in the high pressure hydrogen concentration zone , . <EOS>