6. Reversibility of Disease: Demonstrated a ≥12% reversibility of FEV1 within 30 minutes following 2 inhalations of albuterol/salbutamol inhalation aerosol (if required, spacers are permitted for reversibility testing only) at the Screening Visit. If a subject fails to demonstrate an increase in FEV1 ≥12% then the subject is not eligible for the study and will not be allowed to re-screen. Reversibility values of 11.50 - 11.99 will be rounded to 12. Documented historical reversibility of ≥ 12 % within 3 months of the Screening Visit will be accepted.