Humidifier vs. Diffuser The differences that diffusers are generally smaller devices designed to be used with essential oils while humidifiers are typically larger devices designed to regulate the moisture level in the air. When considering whether to purchase a diffuser or humidifier, note that it's not recommended to use essential oils with a humidifier. So, let's get started. Number 1. What is a diffuser? Diffusers come in a variety of types, shapes and sizes. They are used for diffusing essential oils into the air for aroma therapy purposes. Do not confuse a humidifier with an essential oil diffuser. Diffusers are different from humidifiers in that they are specifically designed to take drops of essential oils, mix the oils with the water in their tanks and distribute. There are four types of essential oil diffusers, the ultrasonic diffuser, nebulizing diffuser, heat diffusers and evaporative diffusers. Number 2. What is a humidifier? A humidifier is a device designed to keep a set level of moisture in the room area. Moisturising the air in a room is needed in dry climates and in some climates when the heat is turned on in the fall and winter time. Dry air can cause problems with dry skin, bacterial and viral problems and make it more difficult for people to fall asleep. Many people use a humidifier for treating the symptoms of colds, flu and sinus congestion. Number 3. Tank size. There are many types of these humidifiers, but in order to help with all the problems dry air can cause, they need a bigger tank than a diffuser. In order to raise the humidity level throughout the entire room, humidifiers need a large water tank usually holding about a gallon of water. By contrast, essential oil diffusers hold a maximum of 305 ml of water if they even hold water at all. You can choose an ultrasonic diffuser to spray mist, but it won't hold nearly as much water as a humidifier. Number 4. Using water. Different types of diffusers have different requirements to function. Not all diffusers use water, so if you're looking to gain the maximum healing properties from your essential oils, you'll want a nebulizing diffuser like the air-powered diffuser. These don't use water at all since they are meant to provide you with the utmost benefits from your oils. If you opt to use a popular aroma therapy diffuser, like the Dutera diffuser and other ultrasonic diffuser, you'll need to use distilled water rather than tap water for best results. The ultrasonic technology creates ultrasonic vibrations through the water that diffuse the essential oils into the air. The ultrasonic diffuser system requires distilled water to ensure there is no mineral buildup, which occurs frequently when tap water is used.