A copier comprises a housing, an image reading section, an image forming section, a paper discharge section, a paper supply section and an ion generating unit. A bluff body which produces vortices, and consequently pressure fluctuations, is arranged in the measuring tube. The splitter is a polarization splitter. The neurological developments, for example, visual development, motor development and language development were enhanced without findings of anthropometric growth faltering or inhibition. The oxygen concentration sensor is determined to be deteriorated when the change time period is greater than the determination threshold.