To OP Georgia Hens:
To help understand what is going on, the droppings your birds leave behind are well......droppings. To be more precise, chicken manure, which when expelled from your birds is both solids and urine combined. So nitrogen rich wet animal waste.
The purpose of litter in any poultry building is to work exactly like a disposable diaper and serves the same purpose. Deep litter is like a heavy duty overnight diaper, but again, serves the same purpose.
But going beyond that, not only do the droppings mix with the litter, done right, they start to chemically interact with it. Start composting.....or more likely rotting in place.
Litter in all its various forms are comprised of something that in a former life was once part of a living plant. Meaning it is a source of carbon (C). Some plants more or less carbon than others. To form compost, carbon sources (your litter) interacts with some form of Nitrogen (N), along with water and air to get the composting process started. The source of N is from your birds......their droppings. Add a little moisture......some comes from the droppings, some from the soil or other, etc. and this gets the slow rot or composting process started. The N that would bleed off as the ammonia you are smelling binds with the C to get this going instead.
Unless and until the litter gets really deep, this is NOT going to be a hot composting process. More like a slow rot. But in any event, with deep litter there is always enough C to bind with whatever N the birds leave to take it all. So there is NO ammonia given off. Only that earthy smell like that of a forest floor. If you do smell ammonia, time to give it a stir, add more carbon or once the diaper is completely soiled, change it.
Now compare that with sand, which is NOT organic. It is a mineral. Never breaks down to combine with anything. It only gets dirty. What you miss when cleaning or what the birds step in over time gets smeared all over the place. In the event it does get wet, droppings only wash off and through the sand to collect and concentrate below, but still giving off plenty of ammonia as it breaks down. And when you do get tired of all that dirty, smelly sand, one gawd awful heavy, wet, smelly mess to muck out and dispose of.
For this reason, I am not a fan of sand for my house or run floor. Have not used it, would never use it as I would expect it to get filthy, nasty and stink like crazy, just as yours is doing.