When I needed to clean a children's mattress, I understood that chemistry should not be used here. I decided to use ecological steam. I treated it with soda, treated the places where the baby's urine was with vinegar a little, and then with a vacuum cleaner and only then with a steam cleaner. https://www.fortador-usa.com/blog/how-to-steam-clean-a-mattress-to-remove-urine-sweat-stains-dust-mites describes how to steam clean mattress . I recommend excellent material.