Using a puffer for asthma during the day in Ramadaan does not invalidate the fast.
The puffer used for asthma does not invalidate the fast because it is a pressurized gas that goes to the lungs, and is not food, and it is something that is always needed, in Ramadaan and at other times.
Fataawa al-Da’wah, Ibn Baaz, no. 979.
See the booklet Sab’oon Mas’alah fi’l-Siyaam (Seventy issues related to fasting).
Shaykh Ibn ‘Uthaymeen said:
This puffer evaporates and does not reach the stomach, so in this case we say that there is nothing wrong with using this puffer when you are fasting, and you do not break your fast by doing that.
Fataawa Arkaan al-Islam, p. 475
The scholars of the Standing Committee said:
The asthma medication that the patient uses by inhaling it reaches the lungs via the trachea and does not reach the stomach, so it is not food or drink or anything of the sort… So it seems that the fast is not broken by using this medicine.
Fataawa Islamiyyah, 1/130
And Allaah knows best.