A hydrogen system including: a hydrogen production apparatus that produces hydrogen; a hydrogen storage apparatus that stores produced hydrogen; a first flow path, wherein hydrogen discharged from the hydrogen production apparatus flows into the hydrogen storage apparatus through the first flow path; a second flow path, wherein hydrogen discharged from the hydrogen storage apparatus flows into a hydrogen-using apparatus through the second flow path; a casing that houses the hydrogen production apparatus, the hydrogen storage apparatus, the first flow path and at least part of the second flow path; a third flow path, wherein hydrogen discharged from at least one of the hydrogen production apparatus, the hydrogen storage apparatus, the first flow path and the at least part of the second flow path flows outside the casing through the third flow path; a first valve provided in the third flow path; and a controller that opens the first valve.