- Non-Asthmatic Participants Procedure: Each non-asthmatic participant will undergo a single MCh challenge, which should take approx. 1-1.5 hrs. This will allow for the generation of a "normal" MCh DRC curve to compare with the asthmatic data. The MCh challenge will be stopped when the response to MCh reaches a plateau, when the participant's FEV1 drops 40% from baseline, when the highest concentration of MCh (128mg/mL) has been administered, or if the participant wishes to stop.