It is very important to remove the moist air that is prevalent in a bathroom, to keep the bathroom free from mold, mildew and odors, bathroom exhaust ventilation fans are suggested. The secret to the installation is not so much the physical mechanical and electrical work required; it is to size the fan properly.
Bathrooms, and to a lesser extent kitchens are quite susceptible to a buildup of moisture and they harbor odors. As a result of the moisture, mold and mildew can easily take hold. This threat must be eliminated to keep the room fresh and odor free. A ceiling mounted exhaust fan is the solution to this problem.
Bathroom exhaust ventilation fans are quite heavy and must be fastened securely to a ceiling joist; the fans are designed with mounting tabs which makes this simple. These fans may or may not be fitted with a light that illuminates the room when the fan is running. Regardless of whether the fan has a light or not, they run off 120 volt household power and they are connected to a switch which is conveniently located just inside the bathroom door. The fan is vented to the outside through an opening which is fed by a flexible tube.
Knowing how they function is the easy part, knowing the right size to buy is a little more complicated. Fans are far from being identical, larger rooms require a fan with higher capacity and conversely a small room only needs a small volume fan. Bathroom exhaust ventilation fans are rated in CFM, cubic feet per minute of air which is taken from the room. For small bathrooms, those which are no more than 100 square feet in floor area the calculation is straight forward, calculate the floor area by multiplying the room length by the width, the resulting number is not only the floor area, it is the size of the fan that is needed in CFM. If the room is 75 square feet, the fan must be rated 75 CFM minimum.
Don’t buy a fan that is not large enough for the job, if the fan is not large enough it will not extract the moisture and odors effectively, this leads to excessive moisture and future problems.