Abstract: An air conditioning system includes: a sensor; an obtainer that obtains information indicating air quality in an indoor space, which is output by the sensor; and a controller that calculates an air quality index based on the information obtained, and controls a ventilator, based on the air quality index calculated. The air quality index is expressed by f(Xn)×g(T, H), where f(Xn) denotes a function with respect to Xn that indicates at least one of a CO2 concentration, a concentration of total volatile organic compounds (TVOC), a concentration of particulate matter (PM), an NOX concentration, an SOX concentration, an O3 concentration, a mold count, or a dust count, and g(T, H) denotes a function with respect to T denoting temperature and H denoting humidity in the indoor space.

Abstract: An air conditioning system includes: a sensor; an obtainer that obtains information indicating air quality in an indoor space, which is output by the sensor; and a controller that calculates an air quality index based on the information obtained, and controls a ventilator, based on the air quality index calculated. The air quality index is expressed by f(Xn)×g(T, H), where f(Xn) denotes a function with respect to Xn that indicates at least one of a CO2 concentration, a concentration of total volatile organic compounds (TVOC), a concentration of particulate matter (PM), an NOX concentration, an SOX concentration, an O3 concentration, a mold count, or a dust count, and g(T, H) denotes a function with respect to T denoting temperature and H denoting humidity in the indoor space.

Abstract: A functional water concentration sensor includes: a light source which emits ultraviolet light; a container capable of holding functional water having a pH between 6 and 9, inclusive, and containing hypochlorous acid and hypochlorite dissociated from the hypochlorous acid; a light-receiving element; and a signal processor. The signal processor calculates the concentration of the hypochlorite in the functional water on the basis of the output signal, calculates the percentages of the hypochlorous acid and the hypochlorite in the functional water on the basis of the pH of the functional water and the dissociation constant of the hypochlorous acid, and calculates the concentration of the hypochlorous acid in the functional water on the basis of the calculated hypochlorite concentration and the calculated percentages.

Abstract: A functional water concentration sensor includes: a light source which emits ultraviolet light; a container capable of holding functional water having a pH between 6 and 9, inclusive, and containing hypochlorous acid and hypochlorite dissociated from the hypochlorous acid; a light-receiving element; and a signal processor. The signal processor calculates the concentration of the hypochlorite in the functional water on the basis of the output signal, calculates the percentages of the hypochlorous acid and the hypochlorite in the functional water on the basis of the pH of the functional water and the dissociation constant of the hypochlorous acid, and calculates the concentration of the hypochlorous acid in the functional water on the basis of the calculated hypochlorite concentration and the calculated percentages.