She is a former cleaning lady who worked at a research lab. One day she accidentally inhaled the fumes of an experimental bathroom disinfectant. The fumes had a strange effect on her and turned her into a cleaning-obsessed villain. She was later recruited by F.O.W.L. for their dastardly plans. She hates, and is even afraid of, dirt. She has a sister named Ample Grime, also a F.O.W.L. agent.
Ammonia reappears in the DuckTales/Darkwing Duck crossover story "Dangerous Currency", with no explanation of how she returned to her normal form, where she is a member of the "League of Eve-il" along with Magica De Spell, Cinnamon Teal and Camille Chameleon. They are in an alliance with the Phantom Blot, the Fearsome Four, and the Beagle Boys. They are also later joined by Negaduck when it is revealed that he is the source of the evil slime Magica and the Blot have been using to take over Duckburg and St. Canard. However, the crossover, which was not approved by Disney, is considered non-canon, so Ammonia's whereabouts following "F.O.W.L. Disposition" are officially unknown as of this writing.