The main purpose of a ventilation fan is to vent unwanted odors, moisture and smoke from indoor spaces out to the outside. This is very important, especially in spaces like kitchens and bathrooms where humidity can cause mold to grow. Ventilation fans help control this problem, and they also keep furniture in good condition. They can be useful in other rooms, too, as they can help to deodorize the home and remove cooking odors from the air.
Is one exhaust fan enough?
Intake and exhaust fans on a computer case are crucial to cooling, and a proper layout is important. The goal is to have slightly more intake fans than exhaust fans, and to have them positioned in such a way that they're directing airflow front-to-back and bottom-to-top. This creates positive air pressure, which reduces "dead spots" in the case where dust can collect, and it prevents the intake fans from drawing dust into the computer through unfiltered openings.
Ventilation fans can also be used in the home to improve indoor air quality, and this is especially important for people who have health problems such as asthma. In homes without sufficient ventilation, indoor odors can linger and furniture can become warped or rotted. A ventilation fan can help to solve these problems, and it is a relatively easy, inexpensive way to keep the air in your house clean.
Bathroom ventilation is especially important, and most building codes require that the bathroom have a bathroom exhaust fan that activates when the humidity sensor detects a high level of moisture or when the bath or shower is in use. This prevents moisture buildup from causing mold and other problems in the bathroom, and it also keeps the room smelling fresh and clean. It is important to have the fan properly installed and vented to the outdoors, as if it's not properly vented, it can send moisture into the attic or crawl space where it can rot wood or cause other problems.