Whether the mold is on porous or nonporous surfaces, probably the most important aspect of cleanup is preventing the mold from reappearing. One of the key conditions that allows mold to flourish is moisture, which can form on surfaces because of a water leak or because of condensation from warm, humid air hitting a cold surface. If there is a leak, you need to fix it. The remedy for condensation, though, isn’t always as obvious. If the mold grew on a wall in a closet in a cold corner of your house, try increasing ventilation by clearing out clutter and leaving the door slightly ajar. Desiccants can also be helpful.