Kristin (and the FML), I'm writing in response to your question about why your fert's potty box smells like ammonia. Basically, it breaks down like this: Urine containes urea, which is the chief byproduct of the metabolism of protein (of which a ferret's diet should almost entirely consist of) and is manufactured almost exclusively by the liver, which dumps the urea into the bloodstream for eventual removal by the kidneys. Urea is toxic to mammals and is constantly being filtered out of the bloodstream by the kidneys. This is why kidney failure is inevitably fatal. Once outside the body of the mammal as a component of urine, urea is used by certain bacteria as a source of energy. The byproduct of these bacteria using urea as fuel is ammonia, the all-too-familiar odor associated with the accumulation of urine. Fresh urine almost NEVER smells ammoniac (unless there's a possible UTI or other bacterial nasty), so chances are the urine's been sitting there longer than it should have. Ammonia is highly soluble in water and dissolves readily in the water which moistens the skin lining the nasal passages and trachea. Dahlman (1963) found that over 70% of the ammonia was absorbed in the nasal passages. He further examined the effect of ammonia on the skin lining the nasal passages. Dahlman found that exposing the lining of the trachea and nasal passages to ammonia caused a severe depression of the normal beating motion of the cilia, tiny, microscopic protrusions that move the mucus, which acts as a sticky "flypaper" to trap airborne dust, bacteria, and other contaminants. Factors which directly determine the amount of ammonia in the atmosphere include temperature, the relative humidity, cage population density and the frequency of cage cleaning. Higher temperature and relative humidity mean higher airborne ammonia levels. Ferrets are already prone to colds and other upper respiratory ailments, so it's important to give them as much of a boost in defeating them as possible. Bottom line: Clean the litter box AT LEAST every other day, preferably every day, to prevent this odor, and possible upper respiratory trouble in your babies. Just my $0.02. :) Bright blessings, Rhyakat [Posted in FML issue 3344]