This study looks at how safe and tolerable a medicine called **salbutamol** is for people 18 and older who have **asthma**. Asthma is a condition that makes it hard to breathe. Salbutamol helps open up airways, making it easier to breathe. The medicine is given through an inhaler, which is a small device you breathe into. The inhaler uses a **propellant**, a gas that helps deliver the medicine. The study compares two types of propellants: **HFA-152a** and **HFA-134a**.

Participants must have had asthma for at least 6 months and be using certain asthma treatments. They will need to stop using some medications before certain tests. The study will check if participants' breathing improves after using the inhaler.

• The study lasts for 3 months.
• Participants must have stable asthma without recent severe attacks.
• There might be brief stops in some medications for testing purposes.

This study helps understand which inhaler propellant is safer and more comfortable for people with asthma.