Do you have an old, rattling fan in the ceiling of your bathroom? If this is the case, you might not have thought it was a big deal. Do you know what purpose a bathroom ceiling fan has? If not, you might be surprised to learn that it is very important, possibly saving you from serious air-quality and mold issues. One of the main issues with bathrooms is ventilation. Usually, bathrooms are small enclosed spaces and have little or no air-flow. On top of that, there is a lot of moisture in the room, creating an ideal spot for mold to start growing. A good ceiling fan can clear out steam and moisture from the room to prevent damage, but if it is not installed properly, or if it is malfunctioning, it might not serve its purpose.
The fan also needs to be vented straight outside. In some homes, you will find a bathroom fan venting out into an attic or a crawl-space, and this will definitely cause problems with all that added moisture moved to a new area.