Ozone naturally exists in wild environments such as highlands, forests, and lakesides at a concentration of about 0.03ppm, and most people feel refreshed when visiting such places. Japanese OSHM standards require that ozone concentration in a workplace is below 0.1ppm. Even so, this level of ozone concentration will never be reached even when j.air is left constantly ON. In fact, we actually need a small amount of ozone in our environment.