The Different Kinds of Aromatherapy Diffusers
My very first diffuser was a gift from a colleague who I used to create recipes, photos and blog content for. It's a lovely little nebulizing diffuser that is still running now, years after it was given to me. I've since acquired several others and I'm often asked about the differences between them, so I thought I'd go over that a bit today.
Diffusers are an essential oil delivery tool we can use when we have chosen inhalation as our application method. There are several different kinds of diffusers, each with slightly differing advantages. The main goal of a diffuser is to break up the essential oil molecules into smaller particles and deliver them via inhalation (active diffusers) or to act as a surface that releases the molecules into the air (passive diffusers). They are most useful for applications that are targeting the respiratory system and are also helpful for emotionally / energetically supportive blends.
Passive Diffusers
The most simple kind of diffuser is a passive diffuser. A tissue, a cotton ball, a piece of clay or ceramic, a porous stone in a gemstone bracelet…these all act as passive diffusers. If you place a drop of essential oil on them, they will act as a diffuser as the essential oil slowly evaporates from them.
A cotton ball kept inside a small, 1 ounce glass jar can act as a personal passive diffuser. I can place one drop of a custom essential oil blend on a cotton ball in the morning, seal it in a jar, and use it for inhalation sessions several times throughout the day without having to refresh it.
Passive diffusers can also act as great room fresheners. A little tray of clay pebbles on the bathroom counter can passively diffuse essential oil molecules into the bathroom throughout the day to keep it smelling fresh. A drop of black spruce essential oil placed on a facial tissue that I wave through a room as I walk through it will leave the whole space smelling like a forest.
Passive diffusers are very affordable, can often be things that you already have in your home (a clean washcloth, old sock, a piece of fabric, or notecard will work).
Affordability: $
While passive diffusers disperse aromatic molecules naturally, active diffusers do so via some type of mechanism. Let’s look at a few of the most common kinds of active diffusers.
Ultrasonic Diffusers
Ultrasonic diffusers are probably the most popular kind of diffuser available on the market. They use water and ultrasonic vibrations to disperse the molecules of the essential oil into the air via a fine mist. They are easy to find, affordable, and are available in a wide variety of styles so you can choose one that will look nice with your home’s decor.
If you choose to use thick, resinous, or citrus oils in an ultrasonic diffuser, you will want to clean the diffuser with distilled white vinegar or alcohol after each use. (This is a good idea anyway, no matter which kind of essential oils you are using.) You do not want to let the thicker oils sit in the reservoir of the diffuser overnight. It is recommended to avoid using carrier oils in ultrasonic diffusers.
Ultrasonic diffusers produce a fine mist of water and essential oil that is effective for inhalation but is not as potent as the inhalation treatment of a nebulizing diffuser. This allows ultrasonic diffusers to disperse a small amount of essential oil over a longer period of time. They work well for scenting a room without being overwhelming. I generally add anywhere between 5-10 drops of an essential oil or essential oil blend to an ultrasonic diffuser at a time and it might take the diffuser anywhere between 30-60 minutes to fully disperse that amount of essential oil if I were to run it constantly.
Many ultrasonic diffusers have built-in timers that will allow the diffuser to run in intervals – on for a few minutes then off for a few minutes. Most aromatherapists recommend working with diffusers this way rather than allowing them to constantly run. A generally accepted interval schedule would be anywhere between 15 minutes on, 15 minutes off to 15 minutes on, 45 minutes off. Most diffusers do not have timers with these intervals, however, and will usually run for about a minute and then turn off for 1-2 minutes before turning on again.
The thing I like most about ultrasonic diffusers is that we can also use hydrosols in them because they are made to be used with water. Adding a teaspoon of hydrosol to the water in your ultrasonic diffuser can be a great way to work with a more gentle inhalation treatment, which can be much more suitable for sensitive individuals, children, babies, the elderly, and those who want to work with hydrosols instead of essential oils.
The thing I do not like about ultrasonic diffusers is that they always contain plastic. Even when the case is made of ceramic or bamboo, the well that holds the water is made of plastic. Essential oils break down plastic so the two are not a great pairing.
If you thoroughly clean your diffuser after each use, you can help extend the life of its plastic parts.
You can clean an ultrasonic diffuser by filling up the well with warm water and a dash of white vinegar. Make sure your diffuser is unplugged whenever you are cleaning it. Let the vinegar and water mix soak for a few hours. Pour it out and use a cotton swab or a clean washcloth to wipe away any residue that remains; be gentle around the central disk. Rinse the well with cool water and run the diffuser for a few minutes with water only before drying it.
Affordability: $$ – $$$
Nebulizing Diffusers
Nebulizing diffusers also produce a fine mist, but they do not use water like the ultrasonic diffusers do. They also do not use heat. They essentially break up the essential oils into fine particles and send them into the air in a more potent inhalation treatment.
There are several benefits of using this kind of diffuser:
You can get models that do not allow your essential oils to ever come in contact with plastic.
They are more effective for targeted treatments. I love that an inhalation treatment with this kind of diffuser can be accomplished quickly and effectively.
They do not add any extra humidity to the environment, which might be especially important to you if you already live in a humid area.
There are also some reasons why you might not want to use this kind of diffuser:
You need to work with resinous essential oils in your aromatherapy treatment.
Resin-derived essential oils do not play well with this kind of diffuser. You would have better results if you included them in a smelling salts blend or added them to a passive diffuser or ultrasonic diffuser blend (remember to clean it well after using resin-derived essential oils).Your custom blend contains a carrier oil.
Carrier oils are not suitable for use in nebulizing diffusers.There are pets or young children in the room.
The essential oil mist produced by a nebulizing diffuser is quite strong. In just a few moments, the 5-7 drops of essential oil you added to the diffuser for your treatment will be dispersed into the room in very fine particles that can be quite strong and potentially irritating for pets or young children. I recommend using this kind of diffuser in a quiet area away from children or pets. If you can open a window after your treatment, even better.Your main goal is not a targeted inhalation treatment. You just want to lightly scent the room throughout the day.
Nebulizing diffusers go through several drops of essential oil in just a few minutes whereas an ultrasonic diffuser might take an hour to go through the same amount of essential oil and a passive diffuser might be able to carry a scent for several hours. The nebulizing diffuser also produces a much stronger, more concentrated mist and is meant for short-term application sessions, not long-term use throughout the day.
One of my favorite nebulizing diffuser makers is a company called Organic Aromas. I was first introduced to them several years and was so impressed by their diffusers and their commitment to making diffusers that do not allow your essential oils to come into contact with plastics. They have a great page on their website with illustrations to explain exactly how a nebulizing diffuser works. You can see that page here. I also like their travel diffuser, which is made of carbon steel instead of plastic.
Nebulizing diffusers are best suited, in my opinion, to very specific applications. I prefer to use them most often for acute situations or respiratory ailments because they really ‘pack a punch’ when it comes to administering the essential oils. Their use is much more treatment-like.
The units themselves are usually more expensive than ultrasonic diffusers, but since I find them much more effective for certain situations, I think they are worth the extra cost.
The diffuser in the foreground of the photo below is an example of a nebulizing diffuser.
Affordability: $$ – $$$
Reed Diffusers
Reed diffusers are made of a narrow-necked vase or jar that is filled with essential oil diluted in a lightweight carrier oil or synthetic carrier. Reeds are placed into the jar through the neck and the aroma of the essential oils gradually travels up the length of the reeds and is dispersed into the air. The reeds need to be flipped over occasionally, but this style of diffuser does work well for applications meant purely for enjoyment. I love incorporating them into the decor of a room – you can use any narrow-necked glass or glazed vase to make your own. I often see them in the restrooms at natural foods stores as an alternative to chemical air fresheners.
Reed diffusers are also used to scent spaces with synthetic fragrances.
Affordability: $-$$
Candle / Heat Diffusers
Candle diffusers are usually made out of ceramic, heat-tolerant glass, soapstone, or other natural stone. They usually have a chamber for a tealight candle in the bottom and a bowl that sits on top of that chamber. The essential oil is usually placed into a carrier oil or water in the top bowl and then a tealight is placed underneath the bowl to heat the oil/water, causing the essential oil to evaporate into the room.
There are also other diffusers that work by applying heat via electricity instead of a flame.
Heated diffusers pose a fire hazard and are not generally recommended by most professionals. Aside from requiring a flame to use this kind of diffuser, essential oils are flammable substances.
Affordability: $$ – $$$
Travel / Fan Diffusers
Many of the travel diffusers I have used or seen either plug straight into the outlet in the car or plug into a USB port. Most of them seem to operate via a small fan. Essential oils are placed onto a pad in the center of the unit and then when the unit is plugged into a power source (USB or the car outlet), the fan blows across the pad and distributes the essential oils into the air. I have also come across car units that are essentially mini ultrasonic diffusers and use water with the essential oil.
My favorite travel diffuser is the battery-operated carbon steel nebulizing diffuser made by Organic Aromas. It is the perfect size to fit into a cup holder in a car and is durable enough to pack in your luggage when traveling.
If you are wanting to diffuse essential oils in the car, a clay diffuser charm or cotton ball can also act as a passive diffuser.
Affordability: $-$$
USB Diffusers
USB diffusers are made to be plugged into your laptop or some other device so you can diffuse essential oils near you while you are working at your computer. They periodically send up a little squirt of essential oil mist, much like the scented fragrance units that periodically do the same in public restrooms.
I have not yet found a USB diffuser that works very well or for very long, so I do not generally recommend them. There are other options that are much more effective.
Affordability: $ – $$
Novelty Diffusers
Novelty diffusers can include such things as pens that have a cotton wick inside like an aromatherapy inhaler does, jewelry pieces that have cotton pads incorporated into their design, and other such items. Many jewelry diffusers are made of stainless steel. These are the best options for worn diffusers, as they protect the skin better than a lava bead does.
Affordability: $ – $$
What Do I Recommend?
For most families who are wanting to invest in a diffuser, I would recommend an ultrasonic diffuser. It is generally the most versatile type of diffuser and is the easiest kind to maintain.
For practitioners, those who live in a humid area, those who do not wish to use plastics, or those who deal with a lot of respiratory or sinus ailments, I would recommend a nebulizing diffuser. If you can also afford to invest in a good ultrasonic diffuser, it will give you a bit more versatility.
I also recommend passive diffusing – it is easy, does not require any electricity, and is an accessible method of diffusing for just about everyone because it does not require you to purchase any additional tools.
About the Author
Hi there, I’m Erin! I am the main instructor here at Floranella. I am a clinical herbalist, aromatherapist, artisan distiller and organic gardener based in the Pacific Northwest. Here at Floranella, I teach people how to work with plants safely and effectively from the garden to the apothecary. Thanks for being here! I’m glad you stopped by.
