The smell can be limited by providing a quality diet. Meat source protein will cause a spike in the sharpness of the urine smell. Start with a proper diet & then explore other ways to get it under control.

I used bi-odor (made by Marshall's) for about a year but with suppliers constantly being out of product or the fact that the cost of it doubled since I discovered it, no longer an option. It helped but the cost of continued use was just too much to keep up with it. Great thing to consider if you just have pets or just a few rats. Must provide clean water every day with the proper amount of the additive. Don't just fill up a big water bottle & walk away until empty days later. Even if you don't use an additive,fresh water should be made available every day.

Depending on the type of cage you keep there are ways to control smell. If in more of a pet style set up with levels, frequent cleaning with wiping down the shelves will really help.

Crowding also increases the smell. Depending on the number of animals kept per square foot of living space effects the way you would need to control the odor.