How Long Can Your Bathroom Fan Stay On? Here's The Definitive Answer

There are many benefits of a bathroom exhaust fan, making it an important yet sometimes-underrated part of your home. This mechanical ventilator can help remove less-than-pleasant smells from your commode area, along with pulling out excess moisture to prevent mold and structural damage. Even more, it can clear chemical fumes lingering in the air from cleaning products and reduce condensation that fogs up mirrors after a long shower. While this powerful device is undoubtedly helpful, that doesn't mean you should have it on constantly. So, what is the recommended time to leave a bathroom fan on?

As a general rule of thumb, the bathroom exhaust fan should run for 15 to 30 minutes to help clear moisture or odors from chemical products from the air. If you have a large bathroom or keep the water hot, running it at least 30 minutes is best. Your exhaust fan is the best way to vent a bathroom to keep it mold-free — since excess moisture can promote the growth of unhealthy mold and mildew (and cause paint or wallpaper to peel), pulling this moisture out will protect your home's structure and maintain a healthy environment.

While you might think that leaving the bathroom exhaust fan on for longer times, or even overnight, would be beneficial, think again. In fact, leaving your bathroom fan on for long periods of time can be counterproductive and even dangerous. Not only does leaving the fan on for long periods of time waste electricity and potentially pull conditioned air (heated or cooled) from the rest of your home, but for some older models, it can also accelerate motor wear and even pose a fire hazard.

Bathroom exhaust fans typically rotate between 900 and 2,500 times per minute, helping pull moist or odor-filled air out of the room and vent it to the outside of your home. Running the fan for multiple hours increases the risk of the motor overheating and causing a fire, or of complete motor failure due to accelerated wear. 

To help ensure that you don't leave the fan on for too long, you can install a timer switch. These can be set for the number of minutes of your choosing, ensuring the fan runs just long enough to clear out the excess moisture and odors, but then shuts off automatically to avoid any issues. You can also install a humidity sensor, which turns the fan on when humidity levels are too high and off when the room is dry. To ensure your bathroom fan works properly when on, clean your bathroom vent fan at least once a year to remove any dust and debris.