Detection system and detection method

A detection method for detecting, using a detection system, a substance vaporizing from a detection target,

• the detection system comprising a plurality of detection units, each of the plurality of detection units including:
• a detector configured to detect at least one substance contained in a gas phase;
• a detecting path configured to allow a first gas, containing a substance vaporizing from a detection target, to flow therethrough;
• and
• a cleaning path configured to allow a second gas, not containing the substance vaporizing from the detection target, to flow therethrough,
• the detection method comprising switching an operating state of each of the plurality of detection units from one of a plurality of states to another, and
• the plurality of states including:
• a first state where the first gas is allowed to enter the detector through the detecting path;
• and a second state where the first gas is prohibited from entering the detector through the detecting path, but the second gas is allowed to enter the detector through the cleaning path.