A detection system includes a power generation element; a first outer cover body enveloping the power generation element; a second outer cover body located between the power generation element and the first outer cover body, and enveloping the power generation element; a first space section enclosed by the first outer cover body and the second outer cover body; a second space section enclosed by the second outer cover body; and a detection unit that detects “a gas in the first space section” and “a gas in the second space section.”