It grows on the walls in my little apartment because there isn't proper insulation and the moisture condenses on the cold walls. Plus it is probably coming from behind through the walls, 100 year old building in the Pacific Northwest.

Last year my landlords gave me a dehumidifier and I run that in the closet along with a fan. Hoping that since I started earlier this year with that it will help a lot. I lost some stuff that was stored in boxes in there to mildew different times over the years.

Spraying the walls with straight bleach kills it pretty good though.

Before I got a cat I was diffusing a lot of essential oils in here, I think that helped, but that's bad for cats so I don't do it anymore.