Yes! If all you need is a little extra humidity for a room, running an essential oil diffuser without including essential oils to the water is perfectly okay. Of course, a diffuser will not run as long or put as much water in the air as a humidifier but the diffuser adds moisture to the air.
In this way, can I put essential oils in my humidifier water?
Evaporative humidifiers should NEVER be used with essential oils. Any foreign materials added to the water, such as essential oils, will be trapped by the wicking filter. This will cause the filter to break down and possibly fail. So, no, you can not use essential oils in your evaporative humidifier.
Simply so, is it OK to sleep with a diffuser on?
As long as you’re using a high quality diffuser and high quality,all natural essential or aroma oils, there’s likely no risk to diffusing your oils overnight. However, if you’d like to take extra precautions, the easiest safety solution is to get a diffuser with an automatic shut off feature.