Answered by Shaykh Faraz Rabbani
Question: Scientifically, gas released is actually an aerosol (liquid droplets suspended in a gas). According to the Hanafi school, are these liquid droplets considered part of the gas and thus pure, or are they considered a liquid exiting from one’s rear private part and thus impure? Does one have to clean himself if gas is released?
Answer: Walaikum assalam wa rahmatullahi wa barakatuh,
I pray this finds you in the best of health and spirits.
Legally, that which exits is either gas or filth. If gas, wudu is invalidated, but no cleaning is required. If filth, both cleaning and wudu are called for.
[ref: Shurunbulali, Maraqi al-Falah; Ibn Abidin, Radd al-Muhtar]
And Allah alone gives success.