Why does a spoiled food smell linger even after cleaning?

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

1. 1
   throwing out contaminated items
2. 2
   increasing airflow with windows and fans
3. 3
   scrubbing walls and checking the ceiling
4. 4
   feeding the same food regularly instead of rotating
5. 5
   switching to indoor-specific cat food brands
6. 6
   trying different brands and checking ingredients to avoid allergens or intolerances
7. 7
   Opening windows in the morning and evening
8. 8
   Putting food waste in the fridge or freezer until taking it out of the apartment
9. 9
   Using dehumidifiers, air purifiers, baking soda, and odor absorbers

In their words

Unedited, most upvoted first, each linked to the thread it came from.