French Bulldogs have more sensitive stomachs which means that they do not digest food as good as other dogs and when they can't digest that food as good they have excessive gas in their stomachs.
So that causes French Bulldogs to fart more than other dog breeds and it can make it hard to be around the French Bulldog much unless the dog is outside with you most of the time.
French Bulldogs are good dogs but you must be ready to experience some excessive flatulence which happens sometimes and usually a lot with French Bulldogs.