Do Exhaust Fans Prevent Mold?

To answer the question of: Do exhaust fans prevent mold, we should first look at how these devices work.

And I can assure you that it is not complicated at all. The exhaust fan in the bedroom, or bathroom draws the damp air from the room, and damps it outside. In return, drier air from the outside enters the room through the vents, windows, or doors.

So, do exhaust fans help with mold? By removing the damp air from a room, the exhaust fan can prevent the growth of mold. It can also prevent the breeding of bacteria, as well as mildew. By removing the damp air from the indoor space, expelling it outside, it lowers the humidity considerably. If the humidity stays at the recommended level, toxic black mold, or any other species of the fungus, will not grow.

The exhaust fans work fast, so there is even no time for the moisture in the air to condense. Thus, there is no chance of mold getting a chance to breed.

However, even if you are running an exhaust fan, you should use a hygrometer to monitor the humidity level.

If it goes above 50 percent, you need to switch on your Frigidaire or portable Midea dehumidifier to remove the extra moisture.

How an exhaust fan can help prevent mold

How exhaust fan can help prevent mold

To prevent mold from forming indoors, you need to keep the humidity at 50 percent, or slightly below. In my earlier post on mold humidity growth chart, we said that keeping the indoor humidity above 50 percent can make the mold grow fast. Mold requires food material, moisture and a surface to grow on.

So, how does this fan help to stop mold?

It removes the damp air from your indoor space

When you cook in the kitchen, the damp air stays inside. It recirculates and moves to other rooms, raising the humidity of the entire house.

But an extractor fan can stop this, by removing the moist air, damping it outside. This creates a chance for drier air from outside to enter the room.

Every time you bathe, have a shower or cook, you will generate a lot of steam. This steam circulates in your house, raising the humidity level. To prevent this from happening, the exhaust fan will remove the damp air.

It can lower the indoor temperature

For mold to grow, it requires heat, moisture and nutrients. Also, the temperature and humidity relationship is close.

When the air is warm, it has a higher capacity to hold more moisture. Therefore, it can support the growth of mold. By making the room cooler, the fan lowers the risk of mold development, albeit slightly.

It can help the dehumidifier do a better job

By removing the moist air, the fan can help make the work of the dehumidifier easier. This makes it easier for you, too.

If you are using a portable dehumidifier without a drain hose, the bucket can fill up fast when the humidity is too high.

This means more emptying, or the dehumidifier will just stop working when the bucket is full. Running the fan for 5 minutes only can help move the process of dehumidifying the air forward.

Keeping the air moisture content between 30 and 50 percent prevents the growth of mold.

Do exhaust fans increase humidity?

With prolonged use, an exhaust fan can increase the humidity indirectly. On the contrary, it can help to lower the indoor humidity level a great deal.

However, please note that the outdoor humidity affects indoor humidity. Thus, if the humidity level is high outside, the air coming in through the door, window or ventilation will still be humid.

But an exhaust fan can be like a double-edged sword. You are supposed to use it for a short time. Because using it too long can bring in more humidity. Remember, it damps air outside, so more air from outside can come in. If the air outside the house is humid, you will still be contending with high humidity inside.

When you live in a place like humid Florida, you need to keep an eye on the humidity levels in your house. Therefore, after taking a hot shower, or cooking in the kitchen, you can run the exhaust fan for a few minutes.

It is recommended that you run the fan for five minutes. It will draw the damp air from the indoors to the outside, stopping condensation from happening.

Can no exhaust fan in bathroom cause mold?

Since we have already established that running an exhaust fan can stop mold from growing, you may wonder whether no exhaust fan in the bathroom causes mold.

There is no straight yes or no answer. The reason for saying this is that the lack of a fan does not mean there aren’t other ways to control humidity in the house.

For instance, you could use a basement dehumidifier with drain hose. Get one that is integrated with a humidistat, so that it can turn on and off automatically when need be.

If the basement is really damp, and you have to dispose of the water over a long distance, you can use a dehumidifier with a pump. It will be able to send water over a vertical height.

While running this fan can help to lower the humidity, if there is excess dampness soaked into the walls of the bathroom, it might not be able to dry them.

It cannot do a perfect job of drying the damp walls. Thus, even with the extractor fan working, mold still has a chance to grow.

Even after using the fan in the bathroom, you still should use the best small dehumidifier for the bathroom. It will lower the humidity considerably to a level that cannot support mold growth.

Does exhaust fan reduce room temperature?

An exhaust fan can lower the temperature in the room considerably, thereby making it easier for dehumidifiers and the air conditioner to work.

One of the reasons of installing an exhaust fan in your home is to reduce the humidity, and cool the air. In return, cooling the air makes the environment a bit hard for mold to grow.

Warm air holds more moisture, which can condense easily on surfaces. If there is no condensation, mold is not going to grow.

Running an exhaust fan does not mean that you won’t need to run the air conditioner or the dehumidifier. You are only going to run the window exhaust fan for five minutes or so. However, in summer, you would need to run the dehumidifier and the air conditioner for much longer.


There is no doubt that exhaust fans can prevent mold growth. However, do not rely on the fan alone. Rather, you need to run a dehumidifier to keep the humidity between 30 and 50 percent all the time.

Remember to run the exhaust fan for a short time only, the recommended five minutes. Mold requires warmth and high humidity, and a fan can help to reduce the dampness.

Also read my other articles on:

Can Mold Grow At 60 Percent Humidity?

Can A Humidifier Cause Mold In Room?

Is Air Purifier Good For Mold?

How To Remove Mold Spores From The Air In The House

Is Black Mold In Humidifier Dangerous

Can mold cause sinus infection?