Ultrasonic diffusers are the most commonly available, use a small amount of water in a reservoir (which varies in size depending on your diffuser) and release a cold mist of essential oils, plus water, into the air.

dōTERRA Ultrasonic Diffusers include the Petal Aroma Diffuser and the Lumo Diffuser (with a real maple wood base).  They each have different time and light functions and will serve a different room size.

As a rule of thumb, I use approximately 4 drops essential oils total in 80ml of water for areas of about 20-30 square metres in size.  This ratio is wonderful for a regular sized bedroom, bathroom or study.

If using your diffuser in a living room, open plan area or large bedroom you can consider using 8 drops in 160ml of water and this will service an area of up to 50 square metres effectively.

So, the capacity of your diffuser will be determined by the size of the room it's going to live in.

Most, if not all, Ultrasonic Diffusers are made using plastic but not all are manufactured in the same way or have the same functionality!  Some considerations include:

• The type of plastic used.  Essential oils, particularly the citrus varieties, will interfere with the chemistry of certain plastics and draw toxins from them.  If your diffuser is on the cheaper side, chances are the plastics it is made with are not suitable for essential oils and you are essentially diffusing toxins (albeit small amounts) into your home or workplace.  A dōTERRA Ultrasonic Diffuser will only be made from HDPE plastic and will not be broken down with exposure to essential oils.
• The functionality of your diffuser.  Would you like coloured lights, various options for the running times or intermittent diffusion for overnight use?
• The material used in your "wood" look diffuser.  Often the “wood” look Ultrasonic Diffusers will actually just be plastic and not wood at all.

Overall, Ultrasonic Diffusers are a wonderful, safe and effective way to benefit from your oils at home or work.  The amount of oils used is relatively low if you’re concerned about cost or diffusing around young children/pets.  Also, all Ultrasonic Diffusers will turn off when the timer runs out or when the diffuser is empty.

The negative aspects of Ultrasonic Diffusers include:

• The use of water to release essential oils into the air.  This might be a consideration if your home is moisture affected, or it could serve as a plus if your air is dry!  Also, essential oils generally diffuse out during the first 50% of your water level so you are not getting the benefits the entire time your diffuser is running.
• The noise factor.  They will make noise as the water bubbles and is pushed through the plastic reservoir which could be an issue if using the diffuser in the bedroom whilst sleeping.
• You may need two in an open plan living area.  Their reach is not as extensive as a Nebulising Diffuser. 

Nebulising Diffusers

Nebulising Diffusers are by far the most effective way of diffusing essential oils as they operate without the use of heat, water or plastic - only pure essential oils dropped into a glass reservoir!

They use the Bernoullis Principle to diffuse 100% pure essential oil molecules into your spaces and can service rooms of up to 80 square metres - this can be more than twice the Ultrasonic Diffuser reach.

Due to the nature of these diffusers, the output will be much stronger than its Ultrasonic counterpart.  They require more essential oils to run (up to 25 drops) and should not be used for more than 2-4 hours per day in a suitable sized room (that is, approximately 80 square metres).  If using in a small room, the drops can be adjusted accordingly (e.g. 8 drops in a bedroom).

Nebulising diffusers are more expensive and also more fragile due to their materials, but thankfully a broken glass reservoir can be replaced at a fraction of the cost of a complete diffuser.

The Organic Aromas range that I have in stock is of exceptional quality and all have a handmade wood or ceramic base with custom blown glass reservoir.  What's more, they diffuse oils almost silently and come with a Volume adjustment, touch sensor LED light and automatically switch off after 2 hours of intermittent diffusion.

Finally...

All diffusers will require a little regular maintenance to maximise their effectiveness and prolong their life.

Ultrasonic Diffusers can be 1/4 filled with white vinegar and diffused until empty.  Simply wipe with a paper towel and repeat every 1-2 months.  

Nebulsing Diffusers will need a few drops of ethanol diffused every 1-2 weeks and a deep clean of the glass reservoir using warm soapy water every 1-2 months.