Recently it came to my attention that there are many that have trouble remembering to shut off their bathroom ceiling fans. This in itself is a waste of energy true but the larger concern is a fire issue. Bath fans are not made to run continuously. They are to be used for a period of time while exhausting the moisture in the bathroom and then they should be turned off.
There are many variations and models and like everything some models are better than others.
The installation isn’t very hard and they can be either vented through the roof or a sidewall. I do not advocate exhausting under the roof eves as I have seen done. This allows the moisture to re-enter the attic space through the vents. However it is key that the distance from the motor to the exhaust point be as straight as possible and kept to a minimum. The fans are only able to carry warm moist air a certain distance and after that you will be working the motor too much. Which leads us to our next part- fire.
When ceiling fans in bathrooms have to push the air too far and/or are left running for long periods of time, they can over heat and cause fires. The cause can be the motor itself or lint and dust that has been allowed to accumulate within the unit.
So I would urge you to do two things. The first is the easiest. Open up your bathroom ceiling fan and give it a regular cleaning. That will remove the lint and dust trapped in there.
The second is a bit harder and you’ll probably need an electrician. Replace your standard switch(on/off) with a timer that will automatically shut your fan off.
This model fits in the same space as a standard switch and will shut off at predetermined times and it costs under $20.00
Or this model which a bit more expensive but still under $50.00
No matter what choice you make installing a timer as well as cleaning your bathroom ceiling fans are well worth the small expense compared to the potential alternative.