This study is testing two types of inhalers for asthma patients aged 12 and up. **Asthma** is a condition that makes it hard to breathe. **Salbutamol**, a medicine, is being tested with two different chemicals that help push the medicine out of the inhaler: HFA-152a and HFA-134a. The study lasts for three months.

Participants must have asthma for at least 6 months and be using certain asthma treatments. They should not have had severe asthma attacks recently or other lung diseases. Participants need to stop using certain asthma medicines before some tests.

• The study lasts 3 months, and participants must visit the clinic for checkups.
• Participants cannot have had severe asthma attacks or other lung diseases recently.
• Participants should be stable on their current asthma medicine before joining.