1. Uric acid crystals
2. Strong‑smelling sulfur compounds called thiols

You must break down both layers to remove the smell forever.

• What you’ll need White vinegar (9 %)
• Baking soda
• 3 % hydrogen peroxide (H₂O₂) — pharmacy grade
• A few drops of dish‑washing liquid or liquid hand soap
• Paper towels (or, even better, fine bentonite/zeolite cat litter)

1. Step 1. Vinegar soak — dissolves uric acidBlot the fresh spot with paper towels.
2. Tip: Cover it with a thin layer of fine clay cat litter; let it absorb and vacuum it up.
3. Do not rinse with water — that only spreads the urine.
4. Flood the soiled area with white vinegar diluted 1 : 3 with water.
5. Cover with paper or a cloth to keep the liquid from spreading.
6. Let it dry completely.
7. Vinegar neutralises uric acid, but the thiols (the really nasty smell) will still remain.

Step 2. Baking soda — light dustingSprinkle a thin layer of baking soda over the dry vinegar‑treated spot.

(Make sure the vinegar is fully dry; if not, it will neutralise the soda.)

1. Step 3. Peroxide + soap — destroys thiolsIn a spray bottle mix:

• 100 ml 3 % hydrogen peroxide
• 0.5 tsp dish‑washing liquid
• Water to make 200 ml total

1. Shake gently and spray over the baking‑soda layer until it foams.
2. Leave for 2–3 hours.
3. The peroxide–soda reaction releases oxygen, which oxidises thiols into harmless CO₂ and NH₄ — the odor disappears permanently.
4. No rinsing is usually needed. If desired, extract any remaining soap with a wet‑vac.

Result: The smell is gone for good because the urine compounds were chemically broken down, not just masked.