I came across one word that is "gas-bag." Are there any other specific (not slang) words?
The French performer Le Pétomane, was a professional flatulist, who was known by several terms:
From Wikipedia (linked above):
Le Pétomane (/ləˈpɛtəmeɪn/, French pronunciation: [ləpetɔˈman]) was the stage name of the French flatulist (professional farter) and entertainer Joseph Pujol (June 1, 1857 – 1945). He was famous for his remarkable control of the abdominal muscles, which enabled him to seemingly fart at will. His stage name combines the French verb péter, "to fart" with the -mane, "-maniac" suffix, which translates to "fartomaniac". The profession is also referred to as "flatulist", "farteur", or "fartiste".1
I'd call them a fart-arse, a term which has expanded to include a number of other meanings:-
fart-arse (plural fart-arses)
(UK, slang, derogatory) A generic term of insult.
fart-arse (third-person singular simple present fart-arses, present participle fart-arsing, simple past and past participle fart-arsed)
(UK, slang) To waste time or opportunities; to dawdle.