Inclusion Criteria:  Male or female, aged ≥18. Eligible for MCT procedure. The contradictions to MCT are listed as exclusion criteria. Provision of a signed and dated informed consent form. Subject who receives one of the following medications, that decrease bronchial hyperresponsiveness, is required for a washout period, before conducting the MCT: inhaled bronchodilators, oral albuterol , inhaled and oral glucocorticoids, leukotriene modifying agents, theophylline, cromolyn, and anti-histamines due to their anticholinergic effect.  Exclusion Criteria:  Subjects who have known contradictions to MCT, including:  Tolerate inhalation of the challenge agents Low baseline FEV1: Airflow limitations in FEV1 less than 60% predicted or 1.5L (baseline FEV1 of < 1.5 L or < 60% predicted). Spirometry quality: inability to consistently reproduce quality spirometry Cardiovascular problems: recent myocardial infarction within past three months, uncontrolled hypertension, known aortic aneurysm Recent ophthalmologic surgery or patients at risk for intracranial pressure elevation. Pregnancy and nursing mothers: Methacholine is a pregnancy category C drug and it is not known whether it is excreted in breast milk or is associated with fetal abnormalities. Women subjects will be asked to sign a statement, as part of the Informe Consent Form, that they are not pregnant or nursing mothers). Inability to provide informed consent. Known allergic reactions to materials used in the components of the SG, i.e., polyethylene or silicon, or gold, nickel, copper or alloys containing any of the above.