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Pets · 4 min read · 3 October 2026

Why does cat litter smell of ammonia?

How urea in urine turns into ammonia, why the smell gets stronger over time, and what you can do around the litter tray.

NH₃Ammonia

In short

  • 1Fresh urine doesn't smell sharp; the smell starts when bacteria convert urea into ammonia.
  • 2The longer the litter sits, the further the conversion goes.
  • 3Changing the litter often and keeping the area around the tray clean does the most to reduce the smell.

The smell comes from a conversion, not from the urine

Cat urine contains a lot of urea. Urea on its own doesn't smell sharp. Many bacterial species in the environment produce an enzyme called urease, which breaks urea down into ammonia and carbon dioxide. That eye-stinging smell is ammonia.

This conversion takes time. When the tray isn't emptied for a few days, ammonia builds up, the damp litter becomes an ideal environment for bacteria and the smell spreads through the room.

The area around the tray smells too

When a cat steps out of the litter, it carries small bits out on its paws. The mat under the tray, the nearby rug and the bottom of the wall gradually start producing a smell of their own. That's why the smell may not go away completely even after the litter is changed.

To reduce the smell

Trying to mask ammonia with perfume can bother both your cat and you. Cats are very sensitive to smells; they may refuse to use a heavily scented tray.

  1. 01Scoop out clumped litter every day, and empty and wash the tray completely once a week.
  2. 02Wash the mat under the tray regularly.
  3. 03Apply a lightly scented probiotic product around the tray and to the pet's bed; don't spray it on the animal.
  4. 04Put the tray somewhere with good airflow, not inside a closed cupboard.

Questions

Why does cat litter smell of ammonia?
Fresh urine doesn't smell sharp. The enzyme urease, produced by bacteria in the environment, breaks down the urea in urine into ammonia and carbon dioxide. The longer the litter sits, the further the conversion goes and the stronger the smell.
How do I use it for cat litter odour?
Spray around the litter tray and on your pet's bed from 20-30 cm away, and leave to dry. The litter still needs changing regularly; in between, Air Biotics helps reduce how far the smell spreads.
Can I use it in a home with children, pregnancy or pets?
Yes. It is water-based and contains no chlorine, alcohol or propellant. It can be used in babies' and children's rooms, and around pregnant women and pets. Apply it before the child is in the room, not while they are there; don't spray it at the face, the eyes or onto an animal.

Sources

All literature →
  1. 01

    Microbial ureases: significance, regulation, and molecular characterization

    Mobley HLT, Hausinger RP (1989). Microbiological Reviews 53(1): 85-108

    pmc.ncbi.nlm.nih.gov/articles/PMC372718

    Finding · ReviewUrease, an enzyme produced by many species of bacteria, breaks urea down into ammonia and carbon dioxide.

These studies were not carried out with Air Biotics. What we say about the product is limited to what is written on its packaging; Air Biotics is not a disinfectant.

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