Inactivation method and inactivation system

An inactivation system for inactivating microorganisms and/or viruses present in a specific space in which a person is present by emitting light into the space, comprising at least one light irradiation device, the device comprising:

• a light irradiation unit comprising a light source emitting light in a wavelength range which inactivates microorganisms and/or viruses;
• and
• a control unit configured to control an irradiation of the light by the light source, wherein
• the control unit includes:
• a detection unit configured to detect a person present in the irradiation space irradiated with the light from the light source;
• an acquisition unit configured to acquire an accumulated irradiation amount which is an accumulated value of an irradiation amount of the light irradiated to a person detected by the detection unit in a period from a predetermined reference time point to a current time point;
• and
• a determination unit configured to determine an allowable maximum irradiation amount which is a maximum irradiation amount of the light allowed in the irradiation space by comparing an allowable limit value (TLV:
• Threshold Limit Value) of an irradiation amount of the light in the wavelength range with the accumulated irradiation amount acquired by the acquisition unit, and wherein
• the control unit controls the light source to irradiate the light into the irradiation space with the allowable maximum irradiation amount determined by the determination unit as an upper limit.