Double-blind study, randomized, controlled, and crossover. Study recruited 30 volunteers with stable asthma aged 8-18 years. Participants will perform lung function as part of the routine follow-up then will receive a Foradil 12mcg either with an Aerolizer (a standard dry powder inhaler) or with the Inspiromatic (an active, breath synchronized innovative inhaler). 3-60 days later participants will receive the same drug through the other inhaler.