In the faraway land of Backeye, people have developed a secretive language called Pasgas. Rather than enunciating words, or forming them with gestures, Pasgas speakers communicate by passing wind. They control the pitch and the duration of each toot, with a single phoneme being able to convey as much meaning as an ideogram (such as chinese characters, or japanese kanji characters) or even a whole sentence.
Pasgas is popular among spies, but serves for other professions as well. Abroad, it can be used to relay messages to fellow captives, a conversation that is silent to all but the initiated. In Backeye, guards can use it as a shibboleth to readily identify foreigners. And in team sports such as volleyball it can be used to coordinate strategy without the need for a team huddle.
My question is: is such a method of communication possible? If not, then why? If it is possible, what kind of training would be required to speak Pasgas?
Edit for clarity: the communication I mention above is acoustic, not smell-based.