Moisture joined with warmth in any environment is the major black mold. Bathrooms, especially showers, are not the only prime locations for mold. The basement, if there is any water leakage, is another common area for black mold to flourish.
Another place to watch out for black mold is your heating and air conditioning system, which is continuously recycling air. If there is moisture in the air, this can lead to moisture inside the system, which can then lead to mold growth. In addition to the mold actually growing within the inside of the system itself, now you have a system that’s spewing out mold spores into your living space. This is why it’s so important to have your system checked and cleaned regularly, or replaced if the system that contains mold.