Keep inside dry and moisture outside.
Mold can be found almost anywhere. Mold can grow as long as moisture and oxygen is present.
It is almost impossible to eliminate all mold and mold spores in an indoor environment. That being said it can be controlled by controlling moisture.
As you can see from the photos when moisture isn't probably dried out of flooring materials mold can go unnoticed until it out of control.
Mold Prevention Tips:
• Fix leaky plumbing and leaks in the building envelope as soon as possible.
• Watch for condensation and wet spots. Fix source(s) of moisture problem(s) as soon as possible.
• Prevent moisture due to condensation by increasing surface temperature or reducing the moisture level in air (humidity). To increase surface temperature, insulate or increase air circulation. To reduce the moisture level in air, repair leaks, increase ventilation (if outside air is cold and dry), or dehumidify (if outdoor air is warm and humid).
• Keep heating, ventilation, and air conditioning (HVAC) drip pans clean, flowing properly, and unobstructed.
• Vent moisture-generating appliances, such as dryers, to the outside where possible.
• Maintain low indoor humidity, below 60% relative humidity (RH), ideally 30 – 50%, if possible.
• Perform regular building/HVAC inspections and maintenance as scheduled.
• Clean and dry wet or damp spots within 48 hours.
• Don’t let foundations stay wet. Provide drainage and slope the ground away from the foundation.