The purpose of this study is to investigate the effects of Fenzian™ treatment on symptoms (such as shortness of breath), lung function (how well the lungs work), and albuterol/salbutamol (rescue medication) use in people with asthma. This will be done by comparing the effects of Fenzian™ treatment to the effects of a sham treatment, which looks the same as the Fenzian™ device but doesn't do anything.