Mistress Carla was dissatisfied with what this guy had done and she needed him to correct his mistakes and his omissions. When he refused to do what she wanted, she had no choice but to punish him. The mistress made him smell farts and she also had him lick her pee before she was done with him. He never messed up again after that for fear of what she would do.
Mistress Carla had her ex wrapped around her fingers. She knew that she could easily do whatever she wanted to him and that is why she used him as bait for what she wanted to do. The mistress conveniently tortured the poor guy by forcing him to smell her ass and wanted to make him lick her asshole but she decided against it at the last minute. It was fun for her but not for him.
Mistress Carla had a servant who was unreliable and she did not like it. She felt that the best way for her to deal with those issues was to use her ass and her farts. So she turned the guy into a fart slave and she choked him with her farts. He tried to plead for leniency but she ignored him and went on with her cruel punishment to ensure it never happened again.
This mistress needed to try farting fetish while she was on her own before she could do it with anyone else. And that is why the mistress had to make sure that she perfected the fetish before she made someone endure the torture and humiliation of it. She recorded herself as she did it so that she could assess her performance and find the best way to go about it.